Effects of suspension on tyres

[Kickstart]

Hi

Does badly set up suspension wreck tyres, or does it make tyres last longer?

After all, if the suspension isn't working well then the tyres are not going to be properly in contact with the ground, and unlikely to be pushed hard enough to really wear rapidly.

All the best

Keith
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[Dom_]

If the suspension isn't set up correctly then the tyres are put under loads which it wasn't designed for, and increase it's wear in certain patterns?

Btw, that was a complete guess and i know feck all about suspension set up.

[Walloper]

Specificaly/technicaly You could induce intermitant wear patches due to wrong dampening.
The rebound would be uneven and so side wall could suffer in lean too.
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[Kickstart]

Hi

Dom_, possible, but that would depend on what those extra loads were. If the tyre is being compressed more (or more cycles) then I can see it building up extra heat.

Walloper, surely any intermitant wear patterns would be so small as to be meaningless, as the distance between them would vary so widely with speed, road surface, etc?

All the best

Keith
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[cunni]

From what i have read recently, it would appear that suspension should be setup for riders weight and type of use.

If the suspension is too hard, then the tyres will try to take over some of the work from the suspension, therefore will be deforming more than usual. this will generate more heat in the tyres and generally will decrease the tyres life and put excess waer on the tyre. Also, you will inadvertantly create a larger contact patch, which as good as it sounds, will also increase wear, but in a non-uniform manner. A bit like squaring your tyres off, but not just in the middle! You miht experiance the bike trying to fall to quickly into turns or you may have difficulty trying to corner at a decent lean angle.

You will also notice the tyre skipps across bump road surfaces more readily, therefore reducing your grip on the carriageway surface. This is all similar to having the suspension setup correctly and the tyre over-inflated!

If the suspension is too soft, then the tyre will still grip the road, it won't deform too much (unless the tyre is too soft also) and will feel real nice, but the tyre again is taking over some of the work load of the suspension. This time, it isn't dealing so well with the weight transferes when accelerating or decelerating. Soft suspension can lead to excess weight beingplace over the front tyre when braking, therefore increasing the likelyhood of the front end sliding out under hard braking. Again, you will loose traction ar the rear with a soft setup, but this is less crutial on the road.

Generally, for regular road use, (read generally legal with some speeding and corner fun) the rear want to be set so as it feels comfortable and yet also feels nicely planted o the road. The fornt would be setup to again feel comfortable, not too harsh, but also to allow the front to soak up bumps without altering the tyre profile.

There is probably someone or somewhere on this site that can tell you the dimensions to measure when setting up suspension to your weight and style, but I must admit, I haven't seen these in ages, so can't really comment. It is a two person job usually, involving measureing static height at the front and rear, height of the bike front and rear when you are on it and something else, but again, I haven't messed with this in a while, so I'll leave it for someone else to take over! Hope that helped?!
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[cunni]

Actually, thinking about your first post, if you are a regular road rider and your suspension isn't so far out that it feels horrible or even dangerous, then it will probably make no different that you will notice, other than it might square off alittle quicker.

unless you want to spend loads of money on this or have your mates over for several hours trying to figure out rebound, compression and pre-load, then i wouldn't bother.

A small amount of bad setup won't make much difference!
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[Kickstart]

Hi

Thanks for that Cunni, but it doesn't really explain why.

I do not see how the tyres will start to take over some of the work of the suspension. I can see that it might deform slightly more, but not sure how critical that is, and would expect the main effect would be the bike being thrown upwards.

Also I cannot see how hard suspension can affect the tyre contact patch (except momentarily hitting a fair size bump), as it still has the same load on it.

[wantser]

I would imagine that it would be the same as on a car.

If you have a hard suspension setup, then the tire will take more of the vibration from the road, more of the tire would spend its time in full contact with the surface, generating more heat. With more force on the tyre and going through the tyre, logic dictates that the tyre will wear quicker.

As long as the suspension is set up correctly on both sides of the wheel/bike then the wear should be equal over the tyre surface.
If you have sepparate dampers on each side (like my CX at the rear) if one is tighter than the other this will effectively cause the wheel to twist ever so slighty over bumps and through corners exurting pressure in unevenly over the tyre causing week points. Not to mention a pig to handle!

Hope this helps

Wantser
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[Walloper]

[cunni]

I went off on a bit of a tangent along the lines of racing, where these very small changes affect your lap times by 0.1 seconds!

Sorry about that.

But hard suspension will make your tyre try to act alittle like suspension. Think about it this way: The front forks are rigid, do not move at all, the tyre is nice and soft. When you crest bumps, your tyre will deform under the load, as you stated above. But instead of simply going back to it's normal shape, it hits yet another. It may never recover to it's designed shape until you come to a halt! As you said, not that critical on the streets!

I wouldn't worry about it, unles you feel unbalanced or dangerous or your tyre is wearing through stupidly fast!
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[Kickstart]

[MarJay]

Keith, I have seen how ovely preloaded bikes can shred tyres compared to those which are set lighter. This is because the tyre slides instead of grips when harsh loads are applied.

This sliding is hardly noticeable and may come under the heading of slippage...

Anyway, I know that when the suspension is properly set up for your weight, tyre life is increased considerably when you thrash the bike.

I have seen this demonstrated in magazine articles, as well as on my own Daytona.
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Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[cunni]

[Shaun]

[cunni]

Maybe he went quicker now it's set up right?!
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[Kickstart]

[cunni]

Hmmmmm, Sounds liek your suspension does need softening up alittle.

I assume it is adjustable on the Bimota?!

I would seriously consider this if grip is compromised in the wet, but saying this, I never felt that great on Dunlops in the wet. Maybe my setup was wrong, maybe it was the tyres?
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[Kickstart]

Hi

These are not just bad in the wet, frightening would be a better description. I am not that keen on Dunlops in the wet and never have been, but then that could be related to my weight and how bikes are normally set up. Have a feeling that is partly why some people get on with particular tyres which others hate.

The back is pretty adjustable (although the spring is probably too stiff for me), but the front isn't particularly.

All the best

Keith
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[Hotdog]

[MarJay]

Keith if you weigh less than 12 stone fully leathered you are supposed to have 20mm of static sag at both ends...

The TT (which is not known as a bike with rock hard suspension) had absolutely no static sag until I introduced some by backing off the preload both ends. This has transformed the bike and now it feels like a magic carpet by comparison.

The bike didn't handle badly before, its just now suited to my weight!
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Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[Kickstart]

[Hotdog]

[Kickstart]

Hi

Sorry, I didn't make my thoughts that clear. I mean with minimal load (because the tyres have almost left the ground) the skidding effect is going to have a similarly minimal effect on heating the tyres.

All the best

Keith
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[cunni]

spinning or skidding a tyre immensly (almost motorcross style) will have a bad effect, but some skidding or spinning can actually keep the carcase of the tyre colder, as the outside takes all the heat, therefore prolonging tyre life! This has been proven by Garry Macoy at GP level and the tyre manufacturers who he worked with!

The reason suspension setup can increase wear on the tyre isn't really about tyres skiding over bumps, it's more about the constant flexure the tyre is under. It will repeatedly change profile and as mentioned above, generate more heat than it is supposed to, therefore over cooking the turkey, or more plainly, making it go off quicker.

By comparison, a racing slick that can be brought by anyone at club level will generally last for only three heat cycles, as opposed to a distance on track. sure, if Rossi used it for 25 laps it would be knackered, but that's due to him knowing how to really rag it and get the grip worn out as well as getting it heated up far too much.

A racing slick can be heated up, used to 3 laps, cooled down three times and it will be useless on the fourth useage. Simply because as the tyre heats and cools, it sets off chemical reactions in the tyre which take it from nice and soft/sticky, to a hard lump of uncompromising rubber that won't grip!

A road tyre is similar in that it too eventually wears out from heat exhaustion, however, most people square them off ages before it would become obvious! The road tyre can take many hundreds of heat cycles. However, it is basically always going off, the reaction doesn't wait until some many cycles to start, it's always happening.

Poor suspension setup will cause additional heat to build off, allowing the tyre to firm up quicker and therefore making it easier for the road to rip the rubber off the main surface. It will wear out quicker! Again though, this will be marginal unless you really know how to work a tyre to it's limits on the road, which ain't advisable!
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