High-speed Front-end wobble / chatter

[sceats]

Above an indicated 90ish mph I get odd vibrations - verging on the chatter - through the front end of my Honda VFR VTEC. They seem to be, for the musical amongst you, almost on a 6/8 time cadence in a very regular manne,r feeling like the forks are compressing and expanding very fast / up and down. There doesn’t seem to be any not sideways movement / on the horizontal which I’ve always associated more with wobble.

I got it badly in France last summer on glass-smooth roads and put it down to a loose head race. This has been tightened but the vibrations haven’t gone / am now noticing on the slightly rougher uk roads (when they’re closed, of course, and such speeds are appropriate….) According to the Honda dealer the race is fine / not shot, so doesn’t need replacing.

Had the front wheel checked last week for balance – completely fine, so not that either.

Non-standard bits that could be at fault are
- An aftermarket MRA Vario Touring screen. This doesn’t seem to have caused it as happens with the spoiler in all positions.
- Risers. I had some small risers fitted to the handlebars 18 months ago to make touring through France & Spain more comfortable, and didn’t notice the problem then. But could be I’m riding a little faster / more confidently now and only just noticed the more skittish / sharper handling?
- Tyre; had a new Pilot Road 2CT fitted about 6 months back. Have same on rear so shouldn’t really cause it.

The 3 above don’t really strike me as certain culprits, but I’m a little technically challenged. Ok, ….a lot.

Whilst it’s not a major issue 90% of the time, it’s annoying for the odd moment now and then when I need to make progress. And will be heading out to the Ring this summer so the ability to make high-speed motorway progress there, and then around the Ring, is rather vital.

Anyone on the forum have any thoughts as to possible causes, and / or rectification?

[lonner]

hi m8

as you have checked the front for balance etc

i would be looking at the rear as 90-100 mph vibes are a rear end thing and front shows at 60-70 mph.

so check shock and rear wheel balance and have a look for any wear in the rear bearings wheel swing arm etc

also check the tire for a slight irregularity in its roundness (sounds silly but does happen) or not quite seated on the rim correctly

[sceats]

great - will do. many thanks mate.

[Shaun]

Are you using matching tyres?

It's unlikely but some tyres can cause problem when they're mis-matched. As said above though, get the rear end checked out as some rear end problems can feel like they're at the front.

[sceats]

Using continental pilot roads 2 front & rear, so don’t think it’ll be that. Will get the rear balance / tyre checked too.

I’d certainly agree on what mixing tyres does to the handling. Due to a puncture on tour once had Bridgestone front, Continental rear and a bike handling like 10llbs of sh1t in a 5llb bag….

many thanks!

[Tristan.]

Check your pressures too, I was getting huge front end wobbles accellerating through 3rd and 4th this weekend, turned out I had a slow puncture in the rear.

[sceats]

Pressures are textbook. Oddly it’s less of a wobble and more of the forks chattering up and down skittishly, with little / no sideways movement of bars.

[krebsy]

I'd check the forks then. Seals, signs of oil seepage, Dampening and preload etc...

K.
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[sceats]

The bike’s in relative good nick (bought 2006 new, 14k miles, well taken care of) and forks seem fine with no damage to seals. When the risers were fitted the shop mentioned they had to change the pre-load so could this be at fault? Maybe differential preload between the forks?

[lonner]

[sceats]

Ah – that might explain it. Will get wheel looked at, regardless of key. It might strike the right chord… boom boom.

Many thanks!

[Pete.]

What you're describing points to an out-of-balance tyre.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[sceats]

Thanks – I certainly hope it’s the tyre and not the shock on the way out; emailed David Silver as they didn’t have a replacement OEM on the site. £499 + VAT for a replacement! OEM, not Ohlins or WP! Feck!

Forgive my ignorance; what’s the procedure for correcting an out of balance rear tyre? Just balancing? Of could it be badly fitted in which case presume procedure is to deflate, refit and cross fingers?

[lonner]

take to tyre place that can do bikes and get it checked

as for the shock hagon £255 and better than oe

[MarJay]

I heard there was an issue with the VFR VTEC engine mounts being torqued in the right order... or am I thinking of the Pan European?
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Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[sceats]

Hadn’t heard that about the VFR; might explain the Pan’s wobble that caused it being removed from Police service, but that’s a whole other contentious subject!

Will go with rear-wheel check, then shock check both with fingers crossed…

[lonner]

hi again


i doubt the shock is done but id want to replace it a 20k as they get soggy and spoil a good handling bike.
when i put a hagon on my vfr 800fi it was a revelation and mine was 16k on a R plate so a lot older and more emulsified

the reason i mentioned it was that as its nearing its service life it will amplify the wheel imbalance so i doubt you will need to shell out for a shock if your watching the pennies

[sceats]

Many thanks indeed for all the help; will start with the tyre and hope that sorts it – and hope the shock lasts a bit longer! But will most likely go with hagon once need to replace it.

Will let you know how it fares!

[sceats]

FWIW: Cured! Took bike back to dealer to look at. Got new set of tyres (BT021s as came fitted with Bridgestones so wanted to revert as close as possible back to original state) and has completely cured it. Rock steady up to 135. (On the straight at Silverstone yesterday!)

So many thanks for all the suggestions; all the comments most appreciated. Most glad to say that it came down to fitting some humble new boots!