Tyre selection and usage - best practices

Introduction

[This entire article is now more or less complete, but there may be further refinements at any time. Therefore, check it out whenever you decide to buy new tyres!]

One of the most common questions about improving vehicle's all-terrain performance and endurance is "what is the most effective modification to apply to my vehicle?". Well, using proper tyres, and using them properly, is arguably the most effective vehicle "mod" for all-terrain use.

Notice: "Most effective" can generally mean in the context of cost, performance, simplicity or endurance. Using proper tyres properly can be the most effective "mod" in all of those ways!

This document includes the following topics:

• 1. Choosing a proper tyre type for the desired usage;
• 2. Choosing a tyre size;
• 3. List of various tyre models with remarks;
• 4. Best practices on tyre usage (wheel rotation, wheel balancing, air pressures, rim and tyre repairs);
• 5. Special situations and combinations;

General remarks

First of all, some basic remarks about using tyres on four wheel drive vehicles:

• 1a. Inherent restriction of most four wheel drive transmission systems (Jimny's included) is that the vehicle has to use all four tyres of the same profile (size). Furthermore, all four tyres should be the same model and have a very similar tread depth (even small differences between rotational friction and wheel circumference among wheels can damage the transmission in the long term). This limits the combinations when choosing (buying) tyres.

• 1b. The stated restrictions also apply to the spare (5th) tyre, which must not be overlooked! Topic of spare tyre utilization has its own dedicated sub-chapter: Using five identical tyres.

• 2. Frequent checking (and adjusting) of air pressures is much more important for all-terrain use than for ordinary on-road use, because pressures significantly affect traction as well as the risk of tyre damage.

• 3. Wheel (dis)balancing is a much more prominent issue for all-terrain use, especially for Jimnys as they are notorious for developing a "death wobble" issue. It is a genetic trait derived from their short wheelbase and solid (rigid) front axle suspension design.

• 4. For all-terrain use, higher profile tyres are always preferred against lower profile tyres (a "higher profile" means "taller" tyre). Reasons: higher profile tyres cushion the ride better on all-terrain both for the vehicle and for the passengers, they decrease the chance of rim damage, and they allow better air pressure management. Their only disadvantage is worse performance when the vehicle corners fast in a bend, but it is insensible anyway to do so in a high, narrow, wobbly, jumpy, twitchy vehicle. Therefore, putting oversized rims with thin tyres on a 4WD vehicle is like putting ballet shoes on a village farmer.

Choosing a proper tyre type for the desired usage

Introduction

Tyre designs for passenger and light truck vehicles can be (among other ways) designed and built for regular "on road" use (the vast majority of tyre models) or (to an certain extent) for all-terrain use.

The difference between those two design approaches is not just in the tread pattern (traction capability). Another equally important aspect is tyre's robustness (resistance to various types of trauma, which regularly occurs off the asphalt), which is generally given dedicated design attention for all-terrain tyres (based on tyre's exploitation expectancy). For ordinary road tyres, robustness is barely considered on itself. Also, tyre's adaptability to different weather conditions is also sometimes given more design thought when designing all-terrain tyres.

There is no official standard to differentiate various kinds of all-terrain tyre designs.

There are three "industry categories" of all terrain tyre designs, based on loose practical usage classifications (from "worse" to "best"):

• 1. HT - "Highway Terrain"
• 2. AT - "All Terrain"
• 3. MT - "Mud Terrain"

Tyre manufacturers usually use this classification to position their all-terrain tyre models in their marketing catalogue.

HT tyres generally have the best on-road performance and worst off-road performance of all three categories, while MT tyres generally have the opposite performance characteristics. AT tyres are generally in the middle - being good but not great for both.

Since these are loose classifications, there are "weaker" and "stronger" tyre models in each category, so each tyre model should be precisely evaluated on its own. For example, Dunlop Grandtrek AT20 could be classified either as a "mild AT tyre", or as an "extreme HT tyre" :). Another example is Uniroyal Laredo HD/T, which could be classified either as a "mild MT tyre" or as an "extreme AT tyre".

A special case are retreaded (remoulded, "protect") tyres. Read more about them in the subchapter below.

HT tyre class

• Highway terrain tyres are generally meant to be used predominantly on road, with only slight & light off road excursions (possibly rougher gravel, some grasslands, etc.).
• Their overall tread design and depth is generally quite similar to ordinary road tyres. That means that they generally have equally proficient on-road performance and endurance even for sharp or very fast driving (and similar fuel economy), but almost equally bad all-terrain performance as ordinary road tyres.
• However, having the "terrain" part in their name, HT tyres should be slightly more robust than ordinary road tyres.

Conclusion - for (almost) always on-road driven all terrain vehicles, HT tyres can be an optimal choice if the vehicles are driven sharply or at high speeds. They are always recommended over ordinary on-road tyres for two reasons - they should be more robust and they at least formally "suit" the all-terrain image of the host vehicle.

However, AT tyres are definitely a better choice if proper all terrain driving is even occasionally performed, and/or if the vehicle is not driven fast or sharply.

AT tyre class

• All terrain tyres are generally meant to be used in mixed on-road and all terrain conditions (anywhere between 30% and 70% of time for either).
• They usually have significantly rougher (and a bit deeper) tread design compared to HT and ordinary road tyres.
• They are a performance compromise which is usually hard to achieve.
• They are generally good on-road except for sharp or very fast driving, and generally good off-road except for boggy and/or harsh conditions (deep mud, deep snow, sharp rocks, river crossings ...).
• They are usually significantly more robust than ordinary road tyres.
• They should slightly impact fuel economy.
• They can be a challenge to balance properly.
• Many AT tyres are "all season", which further adds to their "all terrain" value (for example, mountaineers can encounter ice and snow even in June and as early as September).

Conclusion - for all-terrain vehicles which are used for everything - commuting, intercity travel, and various all terrain conditions, AT tyres are the solution. They should not present a jeopardy on the road, and they should be a trusted companion off the road, in the sense of traction and in the sense of reliability.

MT tyre class

• Mud terrain tyres (also called "Maximum Traction") are generally meant to be used predominantly off road, with only slight easy-going on-road excursions.
• They usually have very deep and striking ("tractor looking") tread and sidewall appearance, and very high robustness capability through various reinforcements.
• They excel in boggy and/or harsh conditions (deep mud, deep snow, sharp rocks, tree roots, river crossings, etc.) and offer the best protection against punctures, cuts and chipping.
• However, they are generally noisy on the road, wear faster and present a real jeopardy if not driven slowly and carefully on a wet road and especially on packed snow or ice.
• Also, they usually significantly affect fuel economy. Due to their coarse construction, they can be very hard or impossible to balance properly.

Conclusion - for all-terrain vehicles which rarely touch the asphalt and are used on tough terrain, MT tyres should be the weapon of choice. However, they can be a jeopardy on regular road surfaces and they wear out faster and louder on road. Also, if not balanced entirely, they will cause issues on road.

Retreaded (remoulded, "protect") tyres

A retreaded tyre is a recycled tyre - it is a previously used and worn out tyre, which had its worn tread surface grinded off, and a new tread (which can have completely different pattern from the old one) glued on.

The material of the new tread is specific to the retreading "factory".

Therefore, retreaded tyres are essentially "tyre zombies" - they are old, worn tyre carcasses which have been restitched and brought back to life like Frankenstein.

Retreaded tyres are produced in all kinds of editions and flavors, with their treads typically mimicking a well known brand name tread pattern. They can mimic any tread pattern, either of slick and smooth road tyres, summer or winter tread designs, as well as heavy-duty AT, MT or even more extreme agricultural and industrial tread patterns. They can also be made with a custom tread design of any appearance that you can imagine.

So, retreaded tyres are great because they are very cheap, ecological, and because there is a wide and colorful choice of tread patterns, especially the extreme traction ones.

But there is a cost to pay. Read on.

Bear in mind - if a tread appears the same like from a brand name tyre model, it does not mean that the materials and compositions of the tread are the same.

Also, you hardly ever know which actual tyres were used for resurrection. For all-terrain duty, tyre sidewalls' strength and robustness are equally important as the tread pattern.

There are also horror stories of retreaded tyres failing catastrophically during high speed driving - the tread layer actually glues off from the tyre carcass. The consequences don't look pretty from any angle of view.

Beware that Jimnys (as all vehicles with solid front axles) are highly susceptible to developing a "death wobble" issue produced by disbalance or play in their front suspension (see Death Wobble wiki article). Improper wheel balance is highly likely to trigger it. Retreaded tyres are notorious for being hard or impossible to balance. So beware!

Here is a document (made by forum user Bosanek) which summarises all arguments FOR and AGAINST using retreaded tyres.

Choosing tyre size

Reasons and benefits

Why would you want to change your tyre size?

Well, for all terrain vehicles, the usual strive is to increase ground clearance. Increasing wheel diameter by increasing tyre profile (the second number in tyre size marking) is the most effective way to achieve this. It lifts the entire vehicle (including the axles!), and is dead simple to do for mild increases.

There are additional advantages of increasing the tyre profile ("tyre height") - as mentioned in the "General remarks" chapter.

Note: When a wheel diameter is changed by a certain amount, the vehicle's (and the axles') ground clearance will change by only half as much (by the amount of wheel's radius change) - basic school geometry explains why.

Issues and risks

However, increasing the wheel circumference/radius incurs the following technical issues:

1. The vehicle will accelerate harder / slower and will move faster downhill on engine braking (in any gear);
2. Transmission will have a heavier duty to perform, leading to premature wear in the long term;
3. Fuel economy can be slightly decreased (because of harder acceleration);
4. Speedometer and tachometer measurement will change as much as the circumference has changed;
5. Larger tyres might not fit - they might rub on the bodywork when the wheels are turning or the suspension is compressed on uneven terrain;
6. The larger spare tyre might not fit in its spare position (contact with some vehicle body parts) and/or in its case/cover;
7. Using snow chains can be impossible or risky, because of (much) less available clearance between the wheels and the surrounding bodywork and mechanical components. However, 4WD vehicles might need snow chains only on steep icy terrain, or for plowing very deep snow.

The extent / severity of these issues highly depends on how much the wheel radius has been increased. They should be negligible to slight at most, if you stay roughly within +-3% of the factory size.

Using too wide tyres also induces some of these issues and risks.

Some of these technical issues can be (and usually have to be) remedied in case of significant tyre size increases:

1. Impact on vehicle's acceleration and engine braking can be remedied by altering the transmission gears ("regearing").
2. Regearing the transmission will also remedy the load on some parts of the transmission, but some parts, like the wheel bearings for example, will remain under heavier duty;
3. Tyres can be made to fit properly by two methods - firstly by lifting the vehicle's body or suspension and/or secondly (usually irreversibly) altering the bodywork (trimming the wheel arches, inner arch linings, etc.), the extent of which highly depends on tyre size;
4. In Jimny's case, the larger spare tyre can be made to fit to the tailgate by installing a spacer on the tyre holder, but the spare tyre vinyl cover or hard spare tyre case has to be custom-made (if badly needed);

Some of the mentioned remedies can be quite expensive to apply, and might also imply further modifications. For example, higher suspension lifts require modified radius arm bushes, brake hoses, propeller shafts, adding wheel spacers, buying a new loan at the bank ....

Note: using non-factory tyre size might be illegal or require some vehicle recertification, depending on country or region.

Jimny factory tyre size and approved sizes

The factory tyre size on all Jimnys is 205 / 70 / R15 (except possibly for some JDMs - Japanese domestic models).

According to some South African and Australian forums (example: this forum topic), their local Suzuki dealers' official policy is to allow +-3% variation in wheel diameter. Therefore, if your Jimny is under warranty (or you want to be mechanically moral), +-3% is your expansion border.

Compatible & interesting tyre sizes for Jimny rims

Quick and simple decision

The three most popular, non-extreme size upgrades are to:

1. 205 / 75 / R15 - (ground clearance and tyre's sidewall height increase by cca. 10 mm)
2. 195 / 80 / R15 - (ground clearance and tyre's sidewall height increase by cca. 13 mm)
3. 215 / 75 / R15 - (ground clearance and tyre's sidewall height increase by cca. 18 mm)

However, they may impose certain risks of collisions between tyres and the vehicle body in some vehicle configurations. That mostly depends if the vehicle has 2nd gen. front bumper or not, if it has front mudflaps or not, if wheel spacers are used, etc. The risk is the lowest with the first size in the list, and the highest with the third size in the list.

They will also introduce certain deviations in vehicle's driving characteristics (road handling, acceleration, top speed, engine braking, transmission's stress). However, those deviations range from "negligible" to "small". The first size in the list is the least deviant, as it provides the smallest diameter change, while also keeping the same tyre width.

Bear in mind that while the first size might be allowed by Suzuki (depending on company's regional policy), the second and third sizes are definitely not allowed by Suzuki. Also bear in mind that ANY tyre sizes apart from those which are strictly specified in vehicle's handbook are prohibited in certain countries!

Warning: MT class tyres, and especially "remoulded" (retreaded) tyres, typically deviate significantly from their theoretical sizes (they tend to be quite larger)!

Regarding "tyre vs. vehicle body" collision risks

Sizes 205 / 75 / R15 and 195 / 80 / R15 generally have no risks of collisions with the vehicle's body, with two exceptions:

• If you have a 2nd gen. front bumper (see below), you might have to straighten it if it is sagged, or trim it just slightly (invisibly) on the bottom (simple job with a grinding tool).
• If you have front mud flaps, you might have to trim a plastic spacer behind them by approx 10-15 mm (which is easy to dismount and mount).

Size 215 / 75 / R15 could be more problematic:

• It may require some trimming of the bottom of the front bumper, especially if it is a 2nd gen. bumper.
• Front mudflaps will probably need to be removed.
• The spare tyre might contact with the rear bumper.
• Wheel arch trimming is generally not needed, except if wheel spacers are used without a lift.

This was a quick and simple guide to the issue of tyre sizes.

Thorough consideration

On the other hand, if you want to dig neck deep into the issue of tyre sizes, study this table on Jimny-compatible tyre sizes, which was made by forum user Bosanek.

That table shows all compatible & interesting tyre sizes which fit on Jimny's stock steel and alloy rims. It also contains many compiled remarks of risks and issues for each non-stock tyre size. Those issues are rarely taken into consideration until it is too late!

The availability of different tyre models in desired tyre size will vary significantly. Not all tyres are manufactured in every listed tyre size.

As it is evident from the table, even if you choose to stay within Suzuki's alleged 3% allowed wheel diameter increase, there are several tyre profiles which can be used to achieve the goal of higher ground clearance. It is preferred to achieve the goal by increasing sidewall height (second number in tyre profile sizing code) instead of altering tyre width (first number in tyre profile sizing code). Maximum gain is achieved if both are increased at the same time.

Tyre models in Jimny-compatible sizes

There is a wide variety of HT, AT and MT class tyre models which are available in Jimny-compatible sizes. It would be a pity to use an ordinary limousine road tyre instead!

This table (made by forum user Bosanek) contains the list of all brand-name HT, AT and MT tyres which he has found on the worldwide market.

In addition to the list of tyre models, that table also contains the availability of each tyre model in most popular Jimny-compatible sizes!

Note: A lot of time has been spent populating that table, and adding custom remarks there. The table is still incomplete in some details, but will be updated from time to time. The sizing availability is the most incomplete, as it takes a lot of investigation to fill the required data for each tyre model.

Therefore, once you settle on your desired tyre size, now you can browse through tyre models and choose the one which is available in that size and suits your criteria the best.

Note: Not all of those tyre models in the list are available in sizes which are compatible for Jimny.

User experiences with certain tyre models

Here are three AT tyre models with which Jimny owners have had great or good experiences with:

• Goodyear Wrangler AT/SA+
• General Grabber AT (not AT2!)
• Continental ContiCrossContact AT

All three of those models have proven themselves as being very good on-road in any time of year, while also proving to be rather versatile off road.

Also, General has recently (09/2016) released model AT3, which looks very interesting indeed. Avoid the model AT2, it is very old and deprecated one!

If you insist on heavy-duty off-road performance but still want to retain some on-road credibility, there are three MT class tyre models with which Jimny owners have been relatively satisfied with:

• Bfgoodrich Mud-Terrain T/A KM2
• Hankook Dynapro MT (RT03)
• Kumho Road Venture KL71
• Maxxis Trepador M8060 (Martin Lines comment: I have found these particularly good on a standard Jimny)

There are other good AT and MT tyre brands and models of course.

Using five identical tyres

Buy and use five same (identical) tyres! The spare tyre should not sit idle all the time! That is even written in Jimny's owner manual.

The spare tyre should be actively rotated with the other four. In case of an all-terrain vehicle like the Jimny, that gives you so much benefits, and only one downside - you pay 25% more at once when buying the tyre set.

Here is a document (made by forum user Bosanek) which shows the rotation scheme, and also lists "FOR" and "AGAINST" reasons to actively use all five identical tyres in a 5-tyre rotation scheme.

It is a good practice to rotate the tyres with every engine oil change. If you recently bought a set of four new identical tyres (they have not got worn more than 1-2 mm at most), you still have time to buy the fifth one (you don't need it yet, until the first rotation).

Warning: If you have a hard or soft spare wheel cover, you won't be able to use it with a spare tyre which is larger than the stock size.

Note: Five-tyre rotation scheme is not practical with tyres which have directional (uni-directional, asymmetric) treads, because each such tyre must be used on only one side of the vehicle for which it was made for. Unidirectional tyres typically have a "Rotation" with arrow mark on their sidewalls, indicating proper orientation. Therefore, when using five tyres, always use non-directional (bi-directional, symmetrical) tyres. Luckily, most HT, AT and MT tyre models have symmetrical treads, but there are exceptions. Beware of this!

Tyre pressures

Learn and use the skills of tyre pressure management.

Changing your tyre pressures to suit the (off)road conditions is the most effective vehicle mod ever!

The benefit is not just for improved traction, but also for improved ride comfort and reduced vehicle stress!

In general terms, reducing tyre pressure by 20-30% from stock on-road pressure is the operating norm for hard (rough) gravel and general off-road conditions. For deep mud, deep snow, sand and other boggy conditions, even more pressure reduction can be used (but with caution).

So, for a Jimny, the stock tyre pressure is 1,6 bar (23 PSI) front and 1,8 bar (26 PSI) rear (some people even it to 1,7 bar on all four tyres).

When driving on gravel roads or general off road, it is completely fine (and even advisable) to reduce the tyre pressure by 25-30% to 1,25-1,15 bar (17 - 18 PSI) - the difference in ride quality is astonishing, while the traction is significantly improved.

Warning: When tyre pressures are reduced, vehicle's top speed should be limited to approx 50 km/h (~ 30 mph) on tarmac roads, or ~ 40 km/h (~ 20 mph) on gravel roads. Otherwise, the tyres might overheat and disintegrate prematurely!

It is compulsory to carry a good quality tyre pressure measurement tool, and very desirable to have your own 12V air compressor.

You can inflate your tyres at gas stations (their equipment is much quicker than your own compressor), but never trust the pressure measurement instruments at gas stations, as they can be wildly inaccurate! Trusting that a publicly (ab)used pressure measurement instrument at a gas station is accurate is like trusting that a prostitute has no STD.

Wheel balancing

Jimnys, as all vehicles with solid front axle suspensions, are susceptible of developing a "death wobble" vibration at a certain speed range.

(Read more about death wobble in Death Wobble wiki article).

Since wheel disbalance can easily cause death wobble, you need to take additional considerations in order to balance your wheels properly.

You can educate yourself about wheel balancing issues at the dedicated chapter "Wheel balancing" of the above mentioned death wobble wiki page: Wheel balancing