wheel alignment question

[andy230]

hi all,

Advice on this observation please?

I checked the wheel alignment yesterday on the racer (SRX chassis with FZR400RR wheels, forks, but SRX swing-arm).

Now here's an interesting thing, and a bit disconcerting.

The centres of the wheels are out by 23mm (front is to the left of the back).

ie.  On the left hand side, the straight edge lines up with both points on the back tyre, and is equally 1mm away from both points on the front tyre.

But on the RHS, touching both points on the back tyre, the front 2 points have an equal 45mm distance between straight edge and tyre.

I think when its been built, its been done to chain alignment, rather than the wheel centres.

Now I know its not ideal, especially for a race bike but is this a significant problem??  My Haynes manual (for the Norton) says "NO" as long the wheels are in line, a little offset doesn't matter.

The handling is in general ok for the road, but its probably a bit under-par for the track, even with the (fairly duff) FZR kit and (adjustable but still lo-tech) twinshock Konis.

We have all heard that the little notches on the swingarm are best ignored, but with the wheels straight, my notches are out by almost 3 (notches)!!!  ie. at "2" on oneside and "5" at the other !!!

Are 20 year old road frames really this inaccurate?  The frame is not bent (wheels are perfect in the vertical axis), just the centres are offset by approx 20 or 25 mm.

Advice, opinions gratefully received!  Will sepeak to the paddock and see what they say at the weekend.

a

[Steve H]

In my opinion that is a Loooooooooong way out., but since you havent noticed it before does it really matter. The point about it being built to line up on the chain sounds about right. By aligning the wheels the way you have then the bike is essentially travelling down the road crab fashion, and again the chain alignment is out.
Its sometimes possible to machine the sprokect carrier/cush drive to move the wheel across, this may mean spacing the caliper carrier on the other side.
If it were me I would either leave it or try and find some monoshock wheels (the chain aligment will stilll be out but not as much)
To align my spoked wheels wheels I worked of the dimensions obtained from the stock wheels.

[srx6]

Im with Steve on this one,the Goose has the same problem but is only 14mm out.I will be machining the rear sprocket carrier and possibly the front sprocket to bring it all into line.

PS good luck at the race meeting

Regards
Alan

[andy230]

Thats what I thought chaps, cheers for the opinions!

However, its not a serious race bike, and is fine for the road -was good to france, scotland, cadwell, etc,, so for just now, I'll blinker myself, and blame my poor lap times on that!!

Hands off the bars it seems to track true, but when you look at it carefully from behind, it looks very odd!

Not ideal...  Maybe time to reconsider bike-wise!

a

[guest27]

Triton wheels are out - had the front dished (spoked wheels) which made it better and noticably better handling.  Lobbed it up the road once which I used to blame on the front wheel being out of alignment with the rear / bike. 

R

[Ken]

Imagine the steering head is twisted (rotated a small amount) Wouldn't this have the same affect. Although your wheels are true with each other. Would it be possible to straightedge your wheels vertically and see if they run the same .
Just a thought

Ken

hi all,

Advice on this observation please?

I checked the wheel alignment yesterday on the racer (SRX chassis with FZR400RR wheels, forks, but SRX swing-arm).

Now here's an interesting thing, and a bit disconcerting.

The centres of the wheels are out by 23mm (front is to the left of the back).

ie.  On the left hand side, the straight edge lines up with both points on the back tyre, and is equally 1mm away from both points on the front tyre.

But on the RHS, touching both points on the back tyre, the front 2 points have an equal 45mm distance between straight edge and tyre.

I think when its been built, its been done to chain alignment, rather than the wheel centres.

Now I know its not ideal, especially for a race bike but is this a significant problem??  My Haynes manual (for the Norton) says "NO" as long the wheels are in line, a little offset doesn't matter.

The handling is in general ok for the road, but its probably a bit under-par for the track, even with the (fairly duff) FZR kit and (adjustable but still lo-tech) twinshock Konis.

We have all heard that the little notches on the swingarm are best ignored, but with the wheels straight, my notches are out by almost 3 (notches)!!!  ie. at "2" on oneside and "5" at the other !!!

Are 20 year old road frames really this inaccurate?  The frame is not bent (wheels are perfect in the vertical axis), just the centres are offset by approx 20 or 25 mm.

Advice, opinions gratefully received!  Will sepeak to the paddock and see what they say at the weekend.

a

[Steve Lake]

mmmm, well, if it's out because of chain alignment, then wouldn't the cheapest option be, to have offset sprockets made?, then get spacers to bring wheels into line, or am i on the wrong tack?

[themoudie]

Andy,

R U Serious? Scrutineering has got to be blind church mice after seeing 'The Light' with Raybans on if they let you out!

Whilst you may have a wierd concoction of bits, nearly 2" 'off centre' on the contact patches will be really...........!

Having thrown the old girl into the kitty litter:

Are the top rear shocker mountings still parallel?
Are the bottom rear shocker mountings still parallel?
Is the swinging arm twisted along its length?
Are the swinging arm arms parallel?
Is the swingarm pivot level throught the frame?
Is the headstock twisted when compared with the swingarm pivot holes?
Is the rear sub-frame twisted away from the centre line of the frame?

Plumb bob, square and or else one of those fairly cheap laser levels from B&Q, Homebase, Wickes etc. needed urgent!

Hands off maybe fine, but then your riding skills and balance compensate the crabbing. Chuck it in at race speed, on the limit of adhesion and you have one very nasty unstable Mother*****, Widow****** thingy.

Sally, with lined up wheels and a 110 front tyre instead of a 100 is twitchy and weavy over grooves and behind other vehicles. My fault, I ordered the wrong size front tyre. Wide wheels/tyres, grippy compounds, and race speeds are probably loading the suspension and frame beyond where they want to go and then to have the contact patches 45mm out of alignment!!!!! Try standard rims  and tyres sizes with some race compound Avons. Might find you could drag the undercart on every corner with a grin.

I'll go away and still wish you well for the weekend.

Cheers, Bill

[Steve Lake]

I'm going to check this out for real this weekend! 2"!!! hell, it must be like riding 2 bikes at once!!

I think i'd rather you were riding my track bike until you sort out this alignment thingy, anyway, we'll chat later today maybe

see you soon

[guest27]

The boys on the RDRZ500 site seem to be keen on changing the wheels / swingarm etc and often raise the question of wheel alignment - feeling there is that if they aint in line they are wrong - guess they should be on a line through the centre of balance / gravity else you will have a yaw rotation about the contact patch on acceleration and braking.  Hot tip there is a laser level rather than a straight edge etc - easier to do the alignment near the centreline of the wheel - where the greater distances from the rim to rim across the wheel lets you se out of alignment for the wheel and not just between wheels.  Guess one of the levels would allow you to check the wheels are upright etc - in relation to the frame.

At the end of the day the only thing that is keeping you on the road is gravity and momentum through the contact patch.

R

[002]

My Personal Opinion Iiis !

   Its Buggered !

You need to sort it out ASAP !

Jethro

[guest27]

Picked up a copy of J Robinson's Chassis tuning bible from ebray.  His thoughts on wheel alignment can be condensed as.  The average Jo - ie me - will wet his knickers if he thinks the new RXCDRR1 has an extra .1% power, or the frame is 0.0000001% stiffer etc, but will not be arsed whether the wheel adjusters are accurate or just hammered out of a lump of tin round the back of some bike shop in the bush.  HOWEVER, the tyres are the most important bit of the bike and to get them to work the wheels need to be aligned properly.  He suggests getting the rear wheel central and using a vernier caliper to do this, and vertical.  Then centre the front wheel on this - make the alignment with bare wheels and across the widest part you can - hard edges and the further you are across the rim the more accurate.  He suggests making up spacers for the front wheel so that where you are measuring the wheel is exactly the same width as the rear - thus no need to guess if you are within an inch or bang on to within .1mm.  Again making sure the front wheel is vertical etc.  Also suggests doing it with no load on the suspension if you can.  Then set up the brakes to align with the caliper / caliper with the rotor etc.  As part of all of this he suggests making sure that the front wheel spacers are bang on and do not cause the forks to deflect at all on fitting and that the bearing is properly supported when it is all bolted down.

Yup this is the concise version and includes none of his calculations...

Great book BTW - does anyone write in any of the comics now with the same level of insight and knowledge.  Closest I can think of is Ash in MCN - and he is Robinson Lite and also factually wrong on a number of occasions that I know of - sooooo



R

[Ken]

Do a search for books by Neil Spalding. I was bought his Moto GP year book for christmas and he has a very good understanding of  chassis and tyres ect. Or try this

http://www.amazon.co.uk/s/ref=nb_ss_w_h_/203-5404425-6800749?url=search-alias%3Daps&field-keywords=motorcycle+chassis

Ken