Front end gremlin

[mattyv74]

Guys, I've discovered a gremlin in the front of my bike.
I've always thought the frontend was really planted on the 7's but mine is giving me grief. The bike feels particularly nervous at high speeds (170+, on the track of course) to the point where I have to back off if the road surface is at all un even.
It is also creating me grief and giving me head shake when I'm committed in a corner and I hit slight wollows in the road.
Every thing seems to check out ok. Every thing is tight, straight, the bearings are fine and fork oil levels seem fine.
I have changed from a 120/70 tyre to a 120/75 to try and get the bike to tip in a bit easier as the 75 gives you a more pronounced crown. I'm also running a 180 on the rear rather than stock 190, which feels ace.
Any ideas guys? Do you think the 75 series would contribute to rhis signicantly? Tyre preasures and balancing are also right.

[Bluefly]

Maybe you're too fat for the bike now you've put all that weight on lately hey buddy?.....

[mfzx6r]

Dear Fat Matt
If you wanted it to turn in quicker and more lighter then you should have gone down in profile in the front.
I'd change all the fork settings back to stock and work from there and replace the oil in the forks with new stuff.

mario

[mattyv74]

[Smitty]

Dear Fat Matt
If you wanted it to turn in quicker and more lighter then you should have gone down in profile in the front.
I'd change all the fork settings back to stock and work from there and replace the oil in the forks with new stuff.

mario

Mario
I agree with your comments
but Matts turn in, is the problem!
To get the shakes as you lean the bike over and the road surface is NOT
like a billiard table...is a problem
and I can understand going to a higher profile to try and stop the shakes, if you are getting that reaction if the road is not smooth.
Matt said...It is also creating me grief and giving me head shake when I'm committed in a corner and I hit slight wollows in the road...
and thats the problem...
as I see it
Matt says bearings and stuff have been checked...
so I agree with you - new oil & go back to stock suspension settings
now
If that all checks out, Matts problems can be faulty suspension or tyres
btw
A pointed tyre is more likely to give the shakes rather than a flatter tyre (irrespective of the aspect ratio)
Matt.... what brand of tyre are we looking at on the front...?
and a long shot...have you checked your swing arm bearings?
and have you softened the rear suspension recently????
(rear end squat will make any tendency to the shakes WORSE!)


cheers

[MadKaw]

To get the bike to turn quicker you go to a higher profile but this will also make the bike less stable as does the 180 rear...
I just changed from 65 series Bridgestone slick to 70 series Dunlop, (used to be 75), and they turn in much better. I was running wide in corners on the 65 series.. The higher profile also gives better side grip..
On a zx7r though they are quite heavy and stable so this shouldn't make that much difference, I agree with the other guys and think you should change fork oil (probly 7.5wt), check the wheel balance and go back to std suspension settings.
Have you raised the rear ride height or raised the forks, it helps to corner but again, will affect stability.

[mattyv74]

Thanks Guys, I'll see what I can sort out on the weekend. I have 70 series on another rim so I'll give that a go aswell.

ps. Sorry Mario, the fingers and axe were aim at blue fly.

[mfzx6r]

Matt
What pressure are you running on the front ??

Fat ? My wife tells me the same all the time !

mario

[Bluefly]

Yeah you guys just let yourselves go in your old age don't ya

Should get the Queer Eye guys in for a KSRC emergency session - you're making the bikes look bad in the member pics....

[Bluefly]

dunno who wrote that - wasn't me! I didn't say nuffin. I've been busy working

[mattyv74]

Hi again guys, Front and rear ride hieghts are stock, althougyh the dampning has been adjusted on the front, but not for a couple of years. So this doesn't explain the recent developement of this shakey stuff.
I check tyre preasures most days that I ride and the 70 series Pilot I run 36psi cold and with the 75 series KR106 (Dunlop slick) I'm running 30 psi cold. Any higher preasure than this on the slick and it won't warm up properly or stay hot. I've only had had the prob for a couple of days, so I don't think the fact it's a slick tyre would contribute to this.
I think I'll change the fork oil and set up the front end from scratch again.

Any body got some thermals they can loan me coz working outside in Ballarat at night is pretty invigourating after all, NOT!!! Fun Fun.

Thanks guys, I'll let you know how I go.

[MadKaw]

The 75 series Dunlop slick is last years model (now replaced by a 70) and was the choice of most superbike teams so that shouldn't be a problem. Depending on the compound and temp you could probly go up a couple of psi. The 950 is soft and can be run at higher psi, the 587 is medium and 701 is hard and 30psi is about right, the hotter the day the more psi you can use but 33 is about the max..
One thing though, you will get less stability out of a slick than a road tyre as they are, well, softer and don't have as much side support.. You are running a slick on the rear as well aren't you...

I hade a 180 rear and 120 70 series front 207gp, with the forks raised in the triple clamps by 7 mm and the rear ride height raised 10mm on my zx7r. Had 7.5 wt fork oil about 5 to 10mm higher than std, preload set for my weight and she handle great...

[Smitty]

snip ..One thing though, you will get less stability out of a slick than a road tyre as they are, well, softer and don't have as much side support.. You are running a slick on the rear as well aren't you.....

think Dave has sorta hit on a possible there...I reckon go up a couple of psi in pressure...and see
are you running these on the road, as well as the tracK?
cheers

yoda

[mattyv74]

Hey Guys, I've been buisey with my study and work so it can take a while for me to reply to you.
Your ideas are greatly appreciated and seem very sound.
Yeah I am running slicks on front and back so they should work together.

Yoda, I'm running these on both road and track. I get em cheap from a guy I know who races a 'Blade'. The bucks I save mean I can actually afford to ride a lot more. I only work part time coz of my studies. It'll be worth it in the long run.

Dave I'm taking your advise and I've organised some 7.5wt oil. But what was oem? My workshop manual quotes 5wt. Does that seem right to you?? When you say it was 5-10mm higher than stock, do you mean the oil level?? Also, when you adjusted the rear ride hieght did you measure the 10 mm at the hieght adjuaster or did measure of the body or frame? If so, where?

You blokes are ace.

[Smitty]

Hey Guys, I've been buisey with my study and work so it can take a while for me to reply to you.
Your ideas are greatly appreciated and seem very sound.
Yeah I am running slicks on front and back so they should work together.

Yoda, I'm running these on both road and track. I get em cheap from a guy I know who races a 'Blade'. The bucks I save mean I can actually afford to ride a lot more. I only work part time coz of my studies. It'll be worth it in the long run.

Dave I'm taking your advise and I've organised some 7.5wt oil. But what was oem? My workshop manual quotes 5wt. Does that seem right to you?? When you say it was 5-10mm higher than stock, do you mean the oil level?? Also, when you adjusted the rear ride hieght did you measure the 10 mm at the hieght adjuaster or did measure of the body or frame? If so, where?
You blokes are ace.

Matt
used slicks...lots use 'em as they are cheap
just have to remember what they are...and the fact they do need warming up a bit...before the big ask...
btw
from memory, OE is 5w oil....some go to 7.5, I personally prefer 10w
(in my ol' jigger, as I don't have the frontend adjustability of the 7r)
and when Dave says 5-10mm..yep the height of the oil is that much higher
than recommended...and I run 8mm higher in mine..helps
firm up the ol' front end....


cheers