Bike weaving at speed

[richierex]

Well I found that the rear tyre valve was dodgy and had around 5psi. Replaced, pumped it up and took it up to Shaftesbury late yesterday afternoon. I ran 36psi front and 40psi rear on the Karoos, they have around 800 miles on them now.
I have Vern's panniers, Touratech top box, 90Kg rider, no pillion. Bike is a pretty standard 1150.
Hit 75 - 80 mark and the problem's gone, so didn't investigate any more. Carrying on with the journey and overtaking a Landrover at about 60+ on a fast B road bend, coming back in across the white line/cat's eyes, tar banding, and the front end tied itself in fukkin knots.
No real drama as it sorted itself out pretty quick, but slightly disconcerting just the same.

So I guess now I'll go back and check the things I was gonna check before I thought I'd cured it with the tyre valve.
Wheel Balance.
Head bearings.

Any other suggestions?
cheers
Millard

I think you have cured it. The original problem was down to the faulty valve in the rear tyre and the problem when crossing white lines, cats eyes and tar banding is fairly normal, especially with dual purpose tyres. Even pure road tyres can give a fair old twitch in certain circumstances.

 

[(RIP) drillam]

I think you have cured it. The original problem was down to the faulty valve in the rear tyre and the problem when crossing white lines, cats eyes and tar banding is fairly normal, especially with dual purpose tyres. Even pure road tyres can give a fair old twitch in certain circumstances.

I take your point Rich, but have ridden two previous GS's on various tyres- all kinda of terrains, including IAM and ROPSA observer on the 1200 with TKC's fitted and I don't tend to bimble, but haven't experienced the kinda reaction I had yesterday during the overtaking experience.
Still as you say - I think it's cured.
Thanks again folks

 

[DrFarkoff]

Millard you said that the rebound screw was almost fully in that's a real bad thing

Basically if you hit a series of bumps the spring was set soft and the rebound near maximum

The spring was not powerful enough to fully extend the spring with the high rebound setting before the next bump so the back end lowers very quickly and it starts to skip as the springing becomes very tense with little or no "travel" A bit like a hard tail

I'd say that was a Major contributor

Did you try the "Foam" trick on the back tyre?

 

[Flanners]

Millard you said that the rebound screw was almost fully in that's a real bad thing

Basically if you hit a series of bumps the spring was set soft and the rebound near maximum

The spring was not powerful enough to fully extend the spring with the high rebound setting before the next bump so the back end lowers very quickly and it starts to skip as the springing becomes very tense with little or no "travel" A bit like a hard tail

I'd say that was a Major contributor

Did you try the "Foam" trick on the back tyre?

Thanks for your settings, I thought my rebound only had a turn of play for setting as it was stuck, I did not realise it had a 3 and a half full turns or more of adjustment. Just set it and the back end is far far better! So thanks.

 

[(RIP) drillam]

Millard you said that the rebound screw was almost fully in that's a real bad thing

Basically if you hit a series of bumps the spring was set soft and the rebound near maximum

The spring was not powerful enough to fully extend the spring with the high rebound setting before the next bump so the back end lowers very quickly and it starts to skip as the springing becomes very tense with little or no "travel" A bit like a hard tail

I'd say that was a Major contributor

Did you try the "Foam" trick on the back tyre?

Doc, sorry for not get back on this. I did read it but then got caught up in other things and forgot about it.
I'll not be able to look at the tyre until next week now, but there's definitely a slow leak somewhere so I'll play around with your suggestion and get it sorted.
Millard

 

[Bendy toy]

Ive got Puncturesafe in my tyres. It will seal small holes but wont mask anything serious. It can also slow the rate of pressure loss if the tyre gets ripped by road debris so you can stop (more) safely.

 

[(RIP) drillam]

All sorted now.

Slow leak done.

A wee bit of wobble in the bars, so I tightened down the head bearing bolt. I hadn't noticed it before, but when wheeling the bike around there was just a wee bit of up and down movement in the ends of the bars.

Suspension behaving itself.

So as I said before, most likely a combination of factors, but it's feeling good now.

Thanks for your help guys

 

[richierex]

I take your point Rich, but have ridden two previous GS's on various tyres- all kinda of terrains, including IAM and ROPSA observer on the 1200 with TKC's fitted and I don't tend to bimble, but haven't experienced the kinda reaction I had yesterday during the overtaking experience.
Still as you say - I think it's cured.
Thanks again folks

It would appear that the new watercooled 1200GS has a problem, seems to tank slap at fast road speeds and also when the rider is standing up at around 45mph. I was wondering if this may have been part of the accident that killed Kevin Ash?