How can you tell when the front spring is shagged?

[adrianw]

Hi,

So what "tests" can I do to check that the front end is still functioning properly?

I'm currently experienceing some interesting handling characteristics from the bike. The back end feels like its sliding about, the missus noticed it felt a bit funny too, alghough she's not on it much.

I even had a definte slide that had my stopping 20 yeards down the road to check I didn't have a flat. (Checked air pressures alls well)

Of course it could just be the shagged Pilot Road that's on it.

But I did have the Maxton shock at the back rebuilt recently (~40K miles on them), however the front wasn't. (I'll do it in the autumn)

So any static tests I can perform that don't involve any spanners etc would be most welcome.

Regards,

Adrian.
R11S 86,000miles

[adrianw]

Oh, by "spring" I mean the whole shock.

Please excuse my blond moments.

Adrian.

[markjenn]

My experience is that anytime you have shagged tires, all handling bets are off. So I'd start there before doing anytihng else. But at 86K, a worn out front shock is certainly suspect, although I wouldn't think it would cause a sliding sensation on the back.

How many miles did you get from the Pilot Roads?

- Mark

[roger albert]

Ditto everything Mark said, including wanting to know the mileage on your pilot roads (just put a rear on myself - I'm going to squeeze another couple thou from my front mac100)

You have to get the tires eliminated as a variable before it's possible to evaluate the shock definitively.

What you can do (not much) is to hold the bike vertical (staning beside it and with it off the stands) and push firmly down on the bars, as if it bounce the front end downwards. You want to look and see if it springs back up instantly (say, a couple tenths of a second) or more slowly (something around a second)

I know that sounds like quibbling and hard for a human to measure, but if you've ever, even once, gotten to do the test on a clapped out and a new shock or fork, you'll immediatley notice the difference. Of course, you''re hoping for the slow response, indicating a modicum or more of remaining low speed rebound damping. This tells you little to nothing about compression damping or high speed damping in either direction.

It's tough to use if you have no experience, but no better time than the present to start building it up.

hope that helps
roger

[adrianw]

Hi,

I'm a bit suspicious about the tyre life, I'd put the current rear as lasting about 3500-4000 miles.

But I'm not convinced that's realistic.

I had to get the rear shock re-built, so it might have been a bit hard on the tyre.

The front has been on since the Begining of the year and needs replaced now, so that must be about 6000 miles.

I'll try and pay more attention with the next set.

Care to comment about the vague line that is running left off center of the tyre?

It only appeared recently, and I wondered if it was linked (another symptom) of what makes it feell like its sliding.

Oh I almost forgot, the bike sometimes creeks when I get off, I can't get it to do it by pushing the back end up and down.

Many thanks.

Adrian

www.octavo2.demon.co.uk/tyre.jpg

[shannonnunley]

Originally posted by adrianw


Oh I almost forgot, the bike sometimes creeks when I get off, I can't get it to do it by pushing the back end up and down.

Many thanks.

Adrian

www.octavo2.demon.co.uk/tyre.jpg

are you sure it's the bike creaking?

[roger albert]

creaking is most often a bit of shifting or vibration of the spring against it's mounts as the suspension is unloaded, or similar in the bushings/mounting bolts. In general, if you can get that to happen by bouncing, you may have a bit of an issue. If you can't, then you're probably ok. Too hard to diagnose tire issues on line, I'm sorry to say. Fairly difficult even off line. You've got to change one or the other and delink/obfuscate things before making good progress.

[Robert Au]

86000 miles on that little island?

Well done.

And I hope you're Rovers and not City!!

[adrianw]

Hi,

Got new rubber fitted.

While I was getting it done we noticed two things:



Where (2) Connects to (1) there is the capacity for some horizontal movement. ie the suspension strut does not fit flush with the rear swing arm/driveshaft where bolt (1) passes through.

Hope that makes sense. Is that normal?

Secondly if you grip the drive shaft about (3) there was some vertical play (audible click).

I that normal?

Finally the bolt (1), does it have a bush or something similar?

Many thanks for idol speculation, or if you've got the full parts catalogue you could look it up....

Adrian.
P.S. My preference would be for Bristol City, not because of any football connotations* but because of the Sweeney esque cockney rhyming slang ie "Tities"

* Too tribal, I'm an evolved human.

have you checked the swingarm and bevel box pivot bearings?

[DavidSoine]

Adrian:

There is a bushing in the swingarm at the lower shock bolt. That is why the shock (clevis) doesn't appear to bolt up flush - the clevis bottoms out on the inner metal sleeve of the bushing.

If there is motion at the rear drive or swingarm, the pivot bearings or swingarm bearings need adjustment or replacement. Loose pivot bearings are a common problem - get them adjusted ASAP.

best,

Dave

[roger albert]

Hi,

> Where (2) Connects to (1) there is the capacity for some
> horizontal movement. ie the suspension strut does not fit
> flush with the rear swing arm/driveshaft where bolt (1)
> passes through. Hope that makes sense. Is that normal?

Yes, it makes sense, and yes, it is normal. Without that axial play, the suspension will bind under any significant side loading, and will eat shaft seals every few tanks of gas.

No worries.

Oh yes, and as DS said, get that rear play out pronto. Play begets more play in a downward spiral.

good luck
roger

[adrianw]

Hi,

Thanks for that insight,

The rear vertical play that I mentioned that you seem concerned with, is that just a case of getting the bush replaced at the (1) / (2) interface?

If so what's it called and I'll get it ordered so the local mechanic can sort it out.

If it's more complicated I'll get some BMW wrench to do it....

All advice gratefully received,

It's my birthday, so I'm off to swallow loads of Kir Royal (missus is plaguing me).

Adrian (33 today)

[roger albert]

I don't believe so. I doubt the 1-2 interface has any vertical play, and it is supposed to have axial play. DS talked about rear pivot play, That can be an adjustment, or the bearing itself. The same can happen in the rear drive's carrier bearing, though that is normally addressable by shimming (as was my own)

Happy B-day and happy swallowing

Kir Royal, that is. What is that stuff?

roger

[shannonnunley]

crown royal?

[adrianw]

Hi,

Kir Royal :

1 Part Cassis + ~5 Parts Champagne

It's an aperitif allegedly

Cassis is some 15% liqueur stuff...

It's great it gets you of your tits real quick....

Sounds like I'm off to some BMW wrench soon...

Regards.

Adrian.
P.S. The JB's on a Linn through AudioLab sounds like the DB's after some Kir Royals.
P.P.S I tried some Australian Fizzy sruff first. But you should really use French Fizzy stuff, it's much better..................

[adrianw]

Hi,

Sorry,
Apparently the Kir Royal should have an 'e' at the end :

"Kir Royale"

Personally I think you should have an 'e' at the begining....

Call me new age,

But I'm off to Glastonbury....

Adrian.

[adrianw]

Hi,

Straight again....

Well, as straight as you can be after 8hrs in the saddle.

Right at the very last moment a BMW dealer did work out that there is a bush at the base of the shock.

If you lifted the rear of the bike with the help of the side stand and let it touch the ground you could hear a slight click.

So while I waited for the part to arrive (it's two metal tubes with some rubber in between) the mechanic went searching for the click.

Turns out that there was some play in the bolt that attaches the shock to the swing arm and this was the source of my irritation.

Never mind, I have the new "bush" now and it will get fitted at the next service.

The bike just did 150 miles at Cadwell Park circuit, without me ****ting myself over the handling. Never mind the Inverness to Bristol run I just done.

So I figure it's fixed for now...

Adrian.