Using different size tyres

[DeeJ]

I have 110/70-17 front, and 150/60-17 rear, fitted as standard.

I was just wondering if it would make loads of difference to use 120/70-17 front and 160/60-17 rear.

I am going to be tracking my bike again, and don't fancy killing my road tyres again, so wanted to get some sticky race tyres, but hard to find for cheap in my size.

I will only be using them for one trackday so a second hand set will do me.

[Guest]

in my experience, if you change one size then the other is effected also. the only one that stays constant is the diameter of the wheel (17"), this is due to the 2nd figure being a % of the tyre... not recommended unless you know what you are doing...

[Guest]

When I used to fit tyres, the suppliers refused to supply me if the knew we were fitting the incorrect size tyre.

Customers used to ask for different sizes, not for price, but for the different handling characteristics.

Therin is the rub, it will affect the handling if they are the incorrect size for the bike/wheel.

For good... or for bad ...

Personally wouldn't recommend it. But, it is possible some feedback from the track guys may point you in the right direction.

[DeeJ]

I've been talking to some track guys.

And they say there is no issue with fitting the larger tyres on road.

But as I intend to use them on the track will mean I will have less contact patch at full lean, and it will low slide without any warning.

150 rear tyre is quite big anyway on a 125cc, just killing me as they are harder to get hold of so dearer.

[Ezituper]

a 120 front tyre will slow your steering thats on the assumption it will fit safely on the width of the front wheel you have.

the higher profile of the rear tyre will quicken up your steering again so maybe cancel out the effects but again is the rear wheel wide enought to accomodate a 160 tyre and is there enough clearance past your chain etc.

If you fir larger width tyres to your wheels you will find the profile of the tyre will be pulled to a rounder shape than the tyres already fitted, this effect really gives you almost no extra contact patch.

Conclusion.

Wider tyres will have little or no effect other than being cheaper.

check the width of your wheel and check with tyre manufacturers to see if their tyres can be fitted to those width rims.

If they say no then don't as tyre fitters will do what you ask so you pay them, should you get any problems they will say they told you not to do it.

[DeeJ]

Been told it will clear the chain, and mudguard with ease.

My front wheel is 3" and rear 4", so are they going to be ok

[Ezituper]

You should really be fine though this is my opinion based on a lot of years motorcycling and messing about with tyre sizes.

Bear in mind you will loose some top end and turn in with larger tyres due to the extra weight which matters more on a 125 than say a 600

With thos e wheel widths you should keep a good tyre profile and so gain contact area wiith the road sorry track

[DeeJ]

You should really be fine though this is my opinion based on a lot of years motorcycling and messing about with tyre sizes.

Bear in mind you will loose some top end and turn in with larger tyres due to the extra weight which matters more on a 125 than say a 600

With thos e wheel widths you should keep a good tyre profile and so gain contact area wiith the road sorry track

 

I am going Donnington next so turn in speed will be slower anyway compared to Mallory.

The only reason I am looking to get bigger tyres is they have given out rain, and I am finding it very hard to get decent tyres in OEM size.

[dex]

i'd probably look for a 120/60 front rather than a 120/70

110/70 has a 77mm sidewall, 120/70 has 84mm, 120/60 has 72mm sidewall.

So the 120/60 sidewall is less different to std than the 120/70, and by being lower it will sharpen up the geometry on the bike slightly. That will help counteract any slowing of steering caused by the wider tyre.

[Stu]

you will get a little less contact patch at full tilt but not sure you will notice too much difference

i know of people racing using that size tyres!