G80 Steering feels vague

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
User avatar
Rob Harknett
Member
Posts: 11236
Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

Re: G80 Steering feels vague

Post by Rob Harknett »

Indeed new tyres of the same names as the old are not the same as the old. 22 psi will look soft and feel soft I use about 25/28 as the tyres vary, They also tend to be smaller than old so often use 3.50 instead of 3.35 IN p[articular the rear.
Sorry if there was a misunderstanding about things to check ,if afore mentioned, read as if was confirming / agreeing.
User avatar
ajscomboman
Member
Posts: 3963
Joined: Mon Jan 01, 1990 12:00 am
Location: HAMPSHIRE UK

Re: G80 Steering feels vague

Post by ajscomboman »

I hate to keep repeating myself guys but as I've mentioned before, the Avon's may appear to be the same as those from years gone by but the make up is dramatically different. The recommended PSI is now 28 front and back with up to 30-32 at the rear with a load on. The need for the higher pressures is the side walls and rubber compound is much softer and grippier than those from the Golden Age.
SPRIDDLER
Member
Posts: 8541
Joined: Wed Sep 01, 2004 1:00 am
Location: WEST SUSSEX UK

Re: G80 Steering feels vague

Post by SPRIDDLER »

G80RIGID wrote:I take the point about worn swing-arm bearings because I have experienced that for myself on other bikes - doesn't apply here of course, but I do remember once having to tighten the central bolt holding front / rear frame sections together !
Ah yes, it's a rigid :oops:
Best way to check if the headstock bearings are loose/worn is to have the front wheel off the ground and put your finger at the point where the lower yoke meets the bottom of the headstock. Any play or bearing looseness will be easily felt as you (or a helper) push/pull back and forth on the fork legs.
'There is a tide in the affairs of men
Which taken at the flood............'
User avatar
Rob Harknett
Member
Posts: 11236
Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

Re: G80 Steering feels vague

Post by Rob Harknett »

ajscomboman wrote:I hate to keep repeating myself guys but as I've mentioned before, the Avon's may appear to be the same as those from years gone by but the make up is dramatically different. The recommended PSI is now 28 front and back with up to 30-32 at the rear with a load on. The need for the higher pressures is the side walls and rubber compound is much softer and grippier than those from the Golden Age.
I'd better up what I use then Rob as I am usually always two up on my bikes. I don't usually go above 30 PSI but some tyres have pretty thin walls. Tyres do seem to vary a lot now. So the guide line can vary by a few pounds of what will suit the bike and its use.
User avatar
Rob Harknett
Member
Posts: 11236
Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

Re: G80 Steering feels vague

Post by Rob Harknett »

If you start with bearings a bit loose, you will actually see movement at the head. Feel movement rocking forks or wheel. Tighten right up. If you fell movement then, its the forks or wheel. That way you can discover better what movement is head bearings.
User avatar
Group Leader
Member
Posts: 538
Joined: Tue Nov 29, 2005 8:51 pm
Location: Herts UK

Re: G80 Steering feels vague

Post by Group Leader »

ajscomboman wrote:I hate to keep repeating myself guys but as I've mentioned before, the Avon's may appear to be the same as those from years gone by but the make up is dramatically different. The recommended PSI is now 28 front and back with up to 30-32 at the rear with a load on. The need for the higher pressures is the side walls and rubber compound is much softer and grippier than those from the Golden Age.
Excellent advice, they are the sort of pressures I run on my 16 with Avons. The first time the pressure in the front tyre dropped to 20 ish (and I hadn't checked it :oops: ) the bike was extremely nervous. So much so, after 3/4 mile I turned around and went home because it was too scary and to try and find out what the heck was going on. Turned out the fix was easy and a very valuable lesson (re-)learnt! :oops: :oops:

Alan
Last edited by Group Leader on Sat Mar 09, 2019 3:49 pm, edited 1 time in total.
1953 AJS 16MS, 1939 BSA 250 and a 1/3 scale Sopwith Triplane but that's another story ..... :lol:
User avatar
clive
Member
Posts: 5657
Joined: Mon Jan 01, 1990 12:00 am
Location: LONDON UK

Re: G80 Steering feels vague

Post by clive »

I would also run the rear tyre at a higher pressure than the front one. 26 with a rigid may be too high. I would try 24 front 26 rear and see if the handling improves. If it does then drop the pressure a lb at a time to improve the ride. Easy thing to try. However if there is clunking from the forks are you undoing the two clamping nuts for the stanchions in the lower yolk when doing the adjustment?
clive
if it ain't broke don't fix
User avatar
Pharisee
Member
Posts: 1126
Joined: Tue Mar 15, 2016 8:51 pm
Location: Lincolnshire UK
Contact:

Re: G80 Steering feels vague

Post by Pharisee »

I run a modern Avon Speedmaster on the front at 28p.s.i and a modern Avon SM on the rear at 32p.s.i.
The bike is a swinging arm G3 dating from 1953. I can tell when its lost a few pounds as it starts squirming around when pushed into fast (a relative term) corners. At the pressures the OP says he's using it would be downright scary!!
I'm from the Fens.... Gimme six.
56G80S
Member
Posts: 3353
Joined: Wed Oct 12, 2005 10:45 pm
Location: N YORKS UK

Re: G80 Steering feels vague

Post by 56G80S »

Rob H, like me you are a relative lightweight. There are many variables.

Group Leader, yes, I've made the mistake of not checking pressures after a little while of not riding and had the same experience. I Had a pump with me fortunately; always have a gauge.

Johnny B
User avatar
ajscomboman
Member
Posts: 3963
Joined: Mon Jan 01, 1990 12:00 am
Location: HAMPSHIRE UK

Re: G80 Steering feels vague

Post by ajscomboman »

56G80S wrote:Rob H, like me you are a relative lightweight. There are many variables.

Group Leader, yes, I've made the mistake of not checking pressures after a little while of not riding and had the same experience. I Had a pump with me fortunately; always have a gauge.

Johnny B
Not that many variables otherwise the manufacturers would have to account for them. They state 28 front and back is normal pressure and for loaded add 2-4lbs at the rear. That's regardless of rider weight, but we won't get into that one, I'm well aware which end of the scale I fall into!! :rofl: :rofl:
Locked