Different tyre profile - OK?

[Pete]

I'm going to put some new tyres on my bike. The recommended size is 180/55 rear and 120/60 front. The tyres I want to put on are the same rear but 120/70 front, so by that I think the profile will be slightly raised. Will this be a problem? Will Jonny Tyre Fitter turn me away? Or is it completely alright (my bike is a Blackbird so usually gets sport touring shoes, I want to give some softer tyres a go so am guessing that's why the profile is raised a bit?).

Thanks all!

[Guest]

I'm going to put some new tyres on my bike. The recommended size is 180/55 rear and 120/60 front. The tyres I want to put on are the same rear but 120/70 front, so by that I think the profile will be slightly raised. Will this be a problem? Will Jonny Tyre Fitter turn me away? Or is it completely alright (my bike is a Blackbird so usually gets sport touring shoes, I want to give some softer tyres a go so am guessing that's why the profile is raised a bit?).

Thanks all!

 

from what i understand the second figure is % of tyre wall, therefore if increase one you have to decrease other..

which is why I could fit 225/50/16 or 205/55/16 to my car, if I increased one, the other had to decrease, something to do with rolling circumference and speedos...

[Guest]

I'm going to put some new tyres on my bike. The recommended size is 180/55 rear and 120/60 front. The tyres I want to put on are the same rear but 120/70 front, so by that I think the profile will be slightly raised. Will this be a problem? Will Jonny Tyre Fitter turn me away? Or is it completely alright (my bike is a Blackbird so usually gets sport touring shoes, I want to give some softer tyres a go so am guessing that's why the profile is raised a bit?).

Thanks all!

why dont you just go for a softer compound, so insead of BT45, BT20

[Guest]

Pete, stick with the recommended tyre sizes. I spent many a joyous time on the phone to suppliers trying to get them to supply different profile tyres for customers bikes. They don't like doing it either. Worst case scenario, it can throw the handling out, and make it unstable to ride.

My advice anyway. I wouldn't.

[Guest]

Pete, stick with the recommended tyre sizes. I spent many a joyous time on the phone to suppliers trying to get them to supply different profile tyres for customers bikes. They don't like doing it either. Worst case scenario, it can throw the handling out, and make it unstable to ride.

My advice anyway. I wouldn't.

 

Although, i have heard generally its a bad idea, i have read about how R1 riders sometimes change down a size for better handling (or something like that) No idea how good it is though, or bad.

Id just stick with recommended tyre sizes for piece of mind

[Guest]

Yep you have heard right Chris, some people like to drop the profile on the front because they have heard it makes the bike 'drop in' easier.

But as with everything, the gain is at a sacrifice of stability. From memory at least. Can't stop people fitting different size tyres, but they are that recommended size for a reason.

[techno]

Dont do it, also with the higher profile will it fit under the mud guard, i had to fit one to the rear of my old bike one time cos of a mix up and it left next to no clearance!

[nigelwood1]

If it is not standard fitment or recomended by manufacturer it will invalidate your insurance.

Try Bridgestone BT021's. they grip fine on the ZZR.

You should be able to get BT016's in the correct size but they may not be recomended for your bike.

[Guest akey]

I wouldn't do it.

You are increasing the rolling diameter of the tyre, that second figure is the height of the tyre as a percentage of the width of the tyre (its not the side wall hight as it is in a car).

My mates got a blackbird and pretty sure you can get BT010's in the right size, and they are pretty sticky.

The increased height will also effect the handling of the bike, and not always in a good way.

[Pete]

All, thanks muchly for the advice. Most revealing! I feel a bit silly now because I got my numbers wrong - the first site I checked said the 'bird wears 120/60 sized shoes and the tyres I wanted are 120/70 hence this post. After checking a few other places it seems the first place I checked had it's numbers wrong as the actual size is 120/70 lol! Just had another look in Haynes and yep, 120/70 is right! D'oh!

So I decided to buy them. Here's the story - I've always had sport touring tyres on, always wondered what a softer compound would be like but couldn't justify the extra cost of a tyre that wouldn't last that long. Then my uncle (also rides) told me about some part-worn ones (I'm talking 2 - 4 laps so hardly worn at all!) on ebay that he was picking up and the guy was selling a few others. He got a Michelin front and something else rear, and he's picked me up a pair of Pirelli Diablo Supercorsas for.....£70! Think I'll wait for the weather to warm up a bit but can't wait to give them a blast.

Thanks again folks.