SV front tyre profile advice

[chickenfunkstar]

Hi,
Its coming close to the time where I need to look at getting a new front tyre.
I was just after advice as to which proflie to get.
At the moment i've got a 120/70/17.

I was of the understanding that there was a tradeoff between stability and quicker turn. I.e. a tyre with a bigger profile will be more stable whilst a tyre will a smaller profile will turn in quicker. Is this correct?

The factory front was a 120/60/17. I was considering going back to this. Would you recomend I do this?

I've noticed that Metzeler make a M1 sportec 120/65/17. Would this be a good compromise?

Thanks,

CFS

[Zapf]

from my limited bike tire understanding but vast cage tire experience...

a taller tire (bigger profile) will able to absorbe more bumps on the road... however because of the increased sidewall hight, it'll also flex more and reduce feed back on a (perfect) flat road. on a non perfect bumpy corner... it might actually be better in floating you over the bumps and be comply more with the surface translating to a more grippy front.

sidewall flex will also reduce steering response... so yes... shorter sidewall (lower profile) will produce a quicker turn in...

also with the overall hight of the tire has the effect of lifting your front suspension... so a higher sidewall means that your front was lifted, than if you had fitted a 60 profile tire translating to slower steering if I understand correctly

[Motoracer]

Long story short, yes a 65 would be a good compramise. :-)

[bane]

Long story short, yes a 65 would be a good compramise. :-)

when you've got time, i'd like to hear the long story MR...

[Motoracer]

when you've got time, i'd like to hear the long story MR...

Hey bane, how's it going man? Haven't seen you in ages. You coming on the ride for this Saturday?

I'm not really a technical person and Zaph's answer seems pretty fancy so mine's probably not going into that much depth but...

Basically I figured, with a 60 profile there is less distance (from the top of the tire to the edge) to be coverd when you are trying to roll the bike to it's side because of the lower profile. So it steers quicker. However this also means that because of the lesser steepness of the tire's curved edges because of the shorter distance from the top of the tire to the edge, you can't lean it around corners to the same degree as you can with a 70 profile.

Same applies to the 70 profile, the tire is obviously bigger so it takes longer time to flick it in and out of corners as the distance to be covered is greater.

Bikes which are meant to have a 60 profile, most of the time you will never use the edge if you use the 70 profile because you don't need that much lean angle and you are having slugish steering for no reason.

Bikes which are meant to have a 70 profile, if you run a 60 profile front and then try to lean the bike as much as you would with a 70 profile, you'll run into the risk of rolling off the edge and lowsiding.

So if you want a compramise to have the quick steering but not give up on too much lean angle, 65 would be good.

At the end of the day different bikes have different geometry so your best bet to get the right tire is to just go with the factory specs. Cause they spend millions on working out what is the best set up for the bike. Some times handeling faults can be corrected by alterations, like changing your tire profile but I don't know about the SV650s handeling charecteristics (never ridden one) to give advise on that.

[FROSTY]

911 is running the 65 profile -bloody nice to turn in
Just a suggestion though--if ya aint got the front end sorted out then it really doesnt matter what tyre ya use cos its gonna patter all over the road

[bane]

Hey bane, how's it going man? Haven't seen you in ages. You coming on the ride for this Saturday?

Been out for a while after an "exit stage left" when confronted by a tractor taking up most of the road :whistle:

however bike and shoulder basically back to OEM condition.

Would love to head out this weekend but have to be somewhere else - hope to catch up soon - hanging out for a good coromandel run- preferably with some 250's i can keep up with (well in a straight line anyways).

[HCW]

Better to stay with manufactuers sugested tyre size and adjust suspension / geometry to suit your needs.

[Motoracer]

Been out for a while after an "exit stage left" when confronted by a tractor taking up most of the road :whistle:

however bike and shoulder basically back to OEM condition.

Would love to head out this weekend but have to be somewhere else - hope to catch up soon - hanging out for a good coromandel run- preferably with some 250's i can keep up with (well in a straight line anyways).

Oh stink... Good luck with that then.

You go very quick through thoes tight and twisty bits, where most of the rider skill shines, so I don't think you'd have any problems holding your own.

Catchya!

[chickenfunkstar]

911 is running the 65 profile -bloody nice to turn in
Just a suggestion though--if ya aint got the front end sorted out then it really doesnt matter what tyre ya use cos its gonna patter all over the road

Yeah true.
There's probably not too much point worrying about the small things when theres bigger things to worry about.

[chickenfunkstar]

Went into cycletreads yesterday and had a chat to them about it.
They recomended that I put a 120/60/17 on unless I knew why the prevoius owner had changed to a 120/70/17. I didn't know why that had been done, so I changed to the smaller profile tyre.

Wow! what a difference. I could tell the difference pretty much as soon as I left the shop. The bars were much easier to turn, felt a bit wierd at first.

Got them fully scrubbed in this morning, so I thought I'd push it a bit on the way home this afternoon. The bike turns in so much easier and I don't have to really muscle it to tighten up my line mid corner. It's given me heaps more confidence through the corners.

Feels like a completly different bike.
Stoked as.

[TwoSeven]

An easy way to calculate the effect of a tire is to look at its height.

A 120/60 has a height of 72mm, a 120/70 has a height of 84mm. For those that dont know how to work it out, the second number gives the height as a percentage of the first number (its width) in mm. So 60% of 120mm = 72mm.

The higher the tire, the less contact patch on the ground and the more it will turn. For the front tire it means that, depending on the trail and tire pressure, stability will decrease as speed gets higher. However, because trail increases due to a higher tire, this characteristic is very dependent on the individual design of the bike.

Likewise with a lower tire, there is more contact patch on the ground and the tire becomes more difficult to turn - again the trail reduces as the height gets smaller.

Note: Its the trail that impacts on the handling of the bike, when you reduce it the bike turns easier at speed, increase it and the bike becomes more stable. As I said, its highly dependent on the design of the bike.

The trail also dictates the range of pressures you can use on the tire. For example, go too low on a low profile tire thats fitted to a bike with a steep head angle and the deformations will cause the wheel to try and turn around (this is head shake).

The other critical setting to factor in is the profile of the rear tire and the setting of your ride height on the rear shock. Both of these will change the angle of attack on the bike which indirectly change the trail on the front tire. So its possible to factor out a change in front tire profile simply by putting the wrong tire on the rear.

At the end of the day given a specific machine it really does come down to preference. I like the bars hard to turn, others like them easy to turn.