G5 rear chaincase rub - Lightweight owners?

BigAl350 · Post by **BigAl350** » Mon Jun 28, 2010 11:38 am

I've just replaced the rear tyre on my 1960 Matchless G5 with something a bit better (Metzeler ME22) than the "John Bull Deep Grip" (=no grip and square profile and many cracks). The bike feels a lot better on it but I noticed that there were rub marks on the rear chainguard. The new tyre didnt seem to touch the case on initial inspection but the clearance was about 1-2mm! After a run, I noticed that the rear tyre WAS contacting the case as there were a few light marks on the tyre's edge. Unfortunately, this ME22 has a slight flare at the tread's end but I'm very surprised at the lack of clearance, thinking something is not right. I've only acquired this bike recently, so I am expecting the worst!

I'd just like to hear from anyone with a Lightweight as to whether they have a similar problem - if not, what sort of clearance do you have between rear tyre and rear chaincase? I'm thinking that either the rear wheel has been built incorrectly or there's a missing/wrong-sized spacer in line with maybe some wheel-bearing wear, although everything in situ looked fine and I could detect no play at all.

The tyre does look like it sits further to the left of the mudguard as well, and the old John Bull has caught the under-mudguard wiring which is on that side.

Any comments gratefully received - would be very pleased to correspond with and meet any Lightweight fans for mutual commisersations, etc (in Reading area).

Al

ajscomboman · Post by **ajscomboman** » Mon Jun 28, 2010 7:00 pm

Al, I am currently running Dunlop K82 universal tyres. I built the wheels in the frame to ensure they were cental. With all that done there is still only 4-5mm clearance between the tyre and the chainguard. I've never had any trouble with rubbing or catching the cables. I would guess that the Metzler is a tadge too wide especially if it's a metric size.

DWS · Post by **DWS** » Mon Jun 28, 2010 7:23 pm

A problem you might have is that most modern tyres are Metric in size and the profiles can be slightly wider than the British equivalent size. I don't know if it is this problem you have but I have experienced the same problem on various bikes myself.

BigAl350 · Post by **BigAl350** » Mon Jun 28, 2010 7:26 pm

Thanks, ajscomboman - but what bike do you have? Is it a Lightweight?

The Metzelers are the correct 3.25 x 18 size but as individual makes of tyres can vary in design, it's hard to know what the clearance will be like if the gap is so relatively tight. I'll probably "adjust" the chaincase slightly to eliminate rubbing and also will make sure it's square on when mounted.

Al

Malleon · Post by **Malleon** » Tue Jun 29, 2010 12:46 am

I would love to see AJScomboman burning up the M3 on a G5 ! Or any other Lightweight for that matter
With due respect, of course...Edited by - Malleon on 28 Jun 2010 11:47:21 PM

ajscomboman · Post by **ajscomboman** » Tue Jun 29, 2010 9:54 am

Al, I have a Mod 8 and Malleon it's a sight to behold if you can catch me that is.

BigAl350 · Post by **BigAl350** » Tue Jun 29, 2010 1:32 pm

Thanks ajscomboman for that. My model 8 is in the shed at my mother's place in Devon, so I'll have a look at the clearance on that one when I'm down there in the next couple of weeks. It's a long way from being back on the road but is nearly complete thanks to the club spares second-hand shelves!

Looking at the G5, it looks like the chaincase is tilting towards the tyre somewhat, so some judicious persuasion may be necessary to restore a few mms gap. More anon - at least it's rideable now without feeling like it's about to throw me off - and I touched 45 MPH on it last night!

Al

Samuel · Post by **Samuel** » Tue Jun 29, 2010 1:58 pm

quote:
and I touched 45 MPH on it last night!

Better keep your hands on the bars at that speed

BigAl350 · Post by **BigAl350** » Tue Jun 29, 2010 8:17 pm

I'm thinking of risking the 27-mile round trip to the Chiltern section on 7 July...hands will definitely be on the bars for that...

BigAl350 · Post by **BigAl350** » Sun Sep 19, 2010 1:57 pm

Well, after much work on the G5 the problem with the chaincase rub is down to the wheel having been built with the wrong offset. Comparing my G5 with my Model 8 and several other 350 Lightweights, my rear wheel rim is 3/8th of an inch too far to the left - hence the rubbing. The front and rear wheels are, of course, out of line too, which may explain the rather nasty handling (as may the knackered steering head bearings and playful swingarm bushes too)! And this bike passed the MoT last year too...

Anyway...for now, I am fitting the rear wheel from my Model 8 into the G5 (the wheel is in fair shape and sits where it should in the swingarm) and I will attempt to move the G5 rim over by spoke adjustment alone - or will go for a rebuild if this fails.

Thanks for the help.