Front Grip

[I'm_a_Newbie]

2 Mornings in a row I have nearly binned the bike on the same roundabout, I could feel the front starting to slide and the bike about to lay down. By reducing throttle and taking off counter steering I managed to pull the bike up again.

About 1 month ago I changed my rear Z6 for a BT021. I still have a Z6 on the front that has done about 5000 miles, so it is now worn flat on the sides, although there is still about 2mm of tread pattern.

It seems the grip in the front does not match that or the rear. (I am really impressed with the grip from BT021).

As the front wears on the sides the contact patch must get bigger so I would have thought grip would have increased.

Either a Z6 front and BT021 rear is not a good combo or my Z6 is shagged!

What do you think? Bad tyre match or shagged tyre?

Thanks
Tim.

[fizzwheel]

Bad tyre match or shagged tyre?

Sounds like a bit of both possibly. Your front sounds knackered, IMHO get it changed ASAP.

[Beenz]

"About 1 month ago I changed my rear Z6 for a BT021. I still have a Z6 on the front that has done about 5000 miles, so it is now worn flat on the sides, although there is still about 2mm of tread pattern."

Do you mean its worn the middle of the tyre?

Once the profile on any tyre has gone, leaning off the perpendicular the wheel gets more and more nervous untill past the middle portion. 5K from a front can shag the profile, certainly considering the less than perfect road surfaces over the winter. As the bike leans the contact patch goes through a reduced level before it rolls onto the good part of the profile.

It's testemant to your riding that you managed to catch a front end slide, quite often that results in a swift journey to the scene of the crash.

I'd change the front boot to match the rear.

[I'm_a_Newbie]

Do you mean its worn the middle of the tyre?

No I mean on the side of the radius, so instead of being a shape similar to this ῼ it starts to look more like ᴧ as the side of the radius wears away.

Tim.

[Beenz]

No I mean on the side of the radius, so instead of being a shape similar to this ῼ it starts to look more like ᴧ although this as the side of the radius wears away.

Tim.

OK, sorry I should have said 'squared off' my comments are the same though. I'd change the front boot to match the rear. Generally I get two rear tyres for each new front, the bike and riding style may dictate otherwise though.

[Luckypants]

My front has gone the same way, leading to some interesting moments. Getting a new pair tomorrow, even though the rear has only 2500 miles on it.

I've gone right off Bridgestones!

[21QUEST]

I doubt it's to do with 'bad tyre match' .
I'm of the school of thought that says "neither the front nor the back knows or cares, what's at each end" mind :D

I cant say if the tyre is significantly worn or not, from your posts but as someone once said to me "if you start asking if it is, it probably is".
Is it okay on other round-abouts? ;) .

Shutting the throttle is probably not what I'll do myself but you got away with it and that's the main thing ... 'good save' :)


Ben

[21QUEST]

......

I've gone right off Bridgestones!

I went of bridgstones years ago. I've never come across a Brand of tyre that cupped(consistently) so badly.


Ben

[I'm_a_Newbie]

I'm of the school of thought that says "neither the front nor the back knows or cares, what's at each end" mind :D Ben

Ok imagine a Sportec Z3 on the rear and a Dunlop D220 on the front, how balanced is that going to be. Or how about D220 rear and Z3 front, that would be a highside waiting to happen!


Is it okay on other round-abouts? ;) . Ben

I don't get to do much riding other than to and from work and this is the only roundabout I use regularly where I get to go most of the way around.

As the roads have been dry for a few days now my speed through corners is picking up again and I am leaning right over.


Shutting the throttle is probably not what I'll do myself but you got away with it and that's the main thing ... 'good save' :)
Ben

I find the engine braking of the SV really good when you need to kill off speed in a bend, as long as you don't close it too quickly or you'll lose traction on the rear as it locks up.

Tim.

[northwind]

021s and Roadtecs have pretty similiar round-shouldered profiles, they should work together pretty well- I ran a roadtec front and 020 rear for a long time and that was also fine. That's a terrible mileage for a Roadtec though, 5000 miles? My last one did about 9000 before i took it off to keep it for a spare, it's still the right shape and working well. You should get more than that from a Sportec or similiar never mind a Roadtec. Makes me wonder about tyre pressures...

[Red Herring]

Front tyres can be a very sensitive thing and a lot of it can be in your mind. Most front tyres wear in the manner you have described (unless you a stunt rider and spend your entire life on the front brake) and as the profile changes it will alter the way the tyre reacts to changes in camber and imperfections in the road surface. Sometimes on roundabouts the front tyre can pick up on the joint between runs of tarmac and as it tries to track away it can give the feel that the front is sliding, even if it isn't. This is especially true if the tyre is worn on the shoulders as instead of having a narrow contact patch the "wider" strip will feel more of the road (a bit like wide low profile tyres do on cars).
My advice is to change the tyre to match the rear, and play around with pressures a little to find a feel you like. There is a lot of opinion that says you shouldn't mis-match tyres, but I do it all the time. However I only do it after starting with a matched pair (a base setting if you like) so that I can then tell if I have made an improvement...or not, with my change.

[Ratty]

I had the same feeling on my SK3 a couple of years ago. I was talking to different people about tyres just like you after 3 (one big) front end slides. Cleaning my bike a couple of days later and came across a nut detached from the lower engine mount behind the gear lever linkage. Only thing keeping the round castellated nut with the bike was a breather pipe trapping it against the end of the thread. Anyway, long story short. Spun it on and tightened it up and handling reverted to normal. Check your engine mount torques, especially if you have had work done like fitting bungs. Worth a try.

Ratty