Tank Slap - Motorcycle Forum

I've seen a decent set of tyres on eBay for the track bike, they are a 120/60 instead of the 120/70 that it's currrently running...

What would be the difference to the handling by dropping the front tyre size down a bit ???

Quicker? I dunno, that's a guess.

You would alter the geometry and sharpen up the steering angle and reduce the trail which would put slight more weight on the front and therefore less on the rear so could have some impact on sag settings due to revised weight distribution. Probably very little impact though and might not even notice the change at the rear. In theory the steering should be quicker because of the above changes but if the tyre has a different profile and is flatter than the one you are removing the two could cancel each other out and result in little or no change to turn in speed.

For clarity the 60 and 70 numbers reference to the height of the tyre not its profile that's why I mention above the 60 tyre could have a flatter profile as less space to be aggressive with a more triangular profile than in a taller 70 section tyre.

Cheers Blade, very useful info.

I'm going to put them towards the top of the shopping list.

See how you get on with them. I have done a lot of trial and error with set up on my sp and its been enjoyable and a good learning experience.

I would experiment with the track bike to constantly work towards evolving a good base set up. Some times we have to go backwards to go forwards but with out trying a change we can't be sure of the exact outcome. I would keep a log of weather, temperature, tyre choice, tyre pressure, suspension settings etc as a minimum so you always have something to refer back too so as to provide some direction going towards. Doesn't have to be motogp levels of data but a few minutes scribbling in a journal can produce some great info IMO.

Makes a lot of sense that mate. I'm going to leave every thing as it is for now, I even asked the seller what tyre pressures he used as he is similar size to me.

The current tyres have a couple of track days in them still , but I'm thinking ahead to next year.

Let us know what happens if you get them Nutz, like Blade I've tried a few different tyres and profiles and found what the bike and I are happy with, but haven't tried a 60 profile front at any time, I'd be really interested to know how you find it. Always room for improvement.

The only bike I know which has a 120/60 as standard is the b1 zx6r as it was never a popular or widely used fitment. Most people who had b1's me included as it allowed a wider choice of rubber opted to fit the more usual 120/70 front tyre.

The 748 came with a 120/60 as standard too. In fact mine still had one on when i bought it.

Changed it to a 120/70 at the first opportunity though. It was a Bridgestone originally and was a horrible tyre.

A small change like that would probably not make much difference. However, I personally would stick with OEM sizes. If you like the way the bike handles/sits why change something that could upset the geometry of the bike?

Cost is a big factor. I want a new(ish) set of tyres for spain next year but can't really justify selling out £200 when I can get something much cheaper.

If a small change in profile won't make a massive difference to the handling, but will make a big difference to my pocket then it's worth a consideration IMO.

I would wait, D6Nutz. There will be a few race scrubs tyres put on ebay over the coming weeks with its being end of season.

I'm not in any rush, just investigating options available. I'll happily admit that I know very little about tyre profiles and how the affect the handling so it's an interesting learning experience for me looking at these things and asking daft questions.

DaytonAndy wrote:A small change like that would probably not make much difference. However, I personally would stick with OEM sizes. If you like the way the bike handles/sits why change something that could upset the geometry of the bike?

Because change can be good and should not be feared. OEM set up is a compromise for a wide variety of factors and considerations.

Its not upsetting the geometry its altering the geometry which could be an improvement or not but you need to experiment with set up or otherwise your stuck with the best you know which is not necessarily the best available.

if you make informed decisions and changes based on proven theory the likelihood of achieving your desired outcome will be greatly improved.

duke63 wrote:I would wait, D6Nutz. There will be a few race scrubs tyres put on ebay over the coming weeks with its being end of season.

Exactly what Duke says. Why buy the first pair you see when you don't need a pair until April ?

Also I wouldn't limit my searching to eBay, speak to people at trackday's, ask people at club racing or use the TD/Race forum classified's as there are plenty of better deals around than what eBay has to offer on scrubs.

What I did when I was doing quite a few TD's on the ZX6 was find a guy with wads of cash who was supporting his son racing and who changed tyres every session. When I needed tyre's I emailed him direct as he always had good quality tyre's for sale and I was always a good customer so the arrangement suited both of us and worked very well.

Motoforum is good.

Thundersport pits, I always saw someone selling tyres and odd bits around the paddock. Then another way to look at it is Spain is not for months yet.
Spending a decent amount of cash to get there, why not have the best rubber you can get for the trip, especially as it's a few days on a nice warm track.

Fwiw an ex-racer that used to frequent 675.cc, gave me a short succinct piece of advice about tyre choice, a real truism tbh.

TYRES=CONFIDENCE

Blade wrote:

DaytonAndy wrote:A small change like that would probably not make much difference. However, I personally would stick with OEM sizes. If you like the way the bike handles/sits why change something that could upset the geometry of the bike?

Because change can be good and should not be feared. OEM set up is a compromise for a wide variety of factors and considerations.

Its not upsetting the geometry its altering the geometry which could be an improvement or not but you need to experiment with set up or otherwise your stuck with the best you know which is not necessarily the best available.

if you make informed decisions and changes based on proven theory the likelihood of achieving your desired outcome will be greatly improved.

I realise that improvements can be had, I personally just don't know enough to even know the likely outcomes of changing profile. That's why I'd stick with oem, I know it works! It could improve turn in massively or maybe ruin stability? Setup seems to be about compromise ie improving one area will likely upset another. I don't want to be barrelling into a corner wondering if I've made the right choice to change my tyre profile!

The front forks on his bike have been dropped by about 15mm so I doubt the profile will matter