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Wheel Alignment
#813084 06/18/20 8:49 pm
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I’ve got a 1951 ZB32 Gold Star, recently bought it so am slowly go in no through the bike top to bottom. Can anyone suggest any techniques for checking wheel alignment? I’ve adjusted the primary chain tension and rear chain so now want to check the alignment.

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Re: Wheel Alignment
Burga007 #813113 06/19/20 3:54 am
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The 'string around the front rim' technique works well - long piece of string looped around the front rim and running back the length of the bike to a few feet behind the rear wheel, about a foot from the ground (enough to clear things on the bike). Easy to see if the front wheel is pointing forwards and whether the rear wheel is pointing in the same direction. Small allowance ended to cater for different tyre sections.

Or

Piece of wood/steel/tube/whetever, long enough to stretch form the front of the front wheel to the rear of the rear wheel, with a small addition at one end to address the difference in tyre section (not all that important though) -alognment errors become obvious. This is the method used for MOT testing in the UK.


No generalisation is wholly true, not even this one.
Oliver Wendell Holmes
Re: Wheel Alignment
Burga007 #813142 06/19/20 12:39 pm
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i use a motipnpro chain alignment tool. it uses the chain itzelf as a line up marker by attaching to the rear sprocket.


every day you do not take a chance is a day of your life that you will never get back.
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Re: Wheel Alignment
Kerry W #813392 06/21/20 11:51 am
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Originally Posted by Kerry W
The 'string around the front rim' technique works well - long piece of string looped around the front rim and running back the length of the bike to a few feet behind the rear wheel, about a foot from the ground (enough to clear things on the bike). Easy to see if the front wheel is pointing forwards and whether the rear wheel is pointing in the same direction. Small allowance ended to cater for different tyre sections.

Or

Piece of wood/steel/tube/whetever, long enough to stretch form the front of the front wheel to the rear of the rear wheel, with a small addition at one end to address the difference in tyre section (not all that important though) -alognment errors become obvious. This is the method used for MOT testing in the UK.

Better done the other way round.
Tie the string o the back wheel then stretch it forward to the front wheel as the back can not move left right like the front can.


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Trevor
Re: Wheel Alignment
Burga007 #813416 06/21/20 3:31 pm
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thjis is the motion pro thing i use. cheap at US$16.99

[Linked Image from i.imgur.com] [Linked Image from i.imgur.com] [Linked Image from i.imgur.com]

mine is older than this one, and doesn't quite fit onto the rear sprocket of a pre-OIF drum rear. dunno about OIF. had to grind a bit of irrelevant metal off it for clearance. but now it works fine and is quick and easy.

the advantage of this tool is that is direct and allows you to align the chain by looking at the chain itself. if the wheel is parallel to the sprocket the wheel will be aligned perfectly when the chain is aligned.

its also good because if you are building something from mismatched parts, it will show when the sprocket alignment is wrong even if the wheels are straight, which a string or a board won't do.

correct alignment with this tool is less than a minute, after you adjust tension.


every day you do not take a chance is a day of your life that you will never get back.
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Re: Wheel Alignment
Burga007 #813420 06/21/20 3:47 pm
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Kevin, thanks for posting the review of the MotionPro tool. I had been pondering buying one but wasn't sure if it was worth it.

I will get one.

John

Re: Wheel Alignment
kevin #813872 06/24/20 11:46 pm
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"after you adjust tension." - just bought the M/Pro can't wait to get - had to do a new rebuilt caliper recently-'78 Triumph style. . BTW - how do you measure the Chain for tension?


1978 Bonneville T140V PX
Re: Wheel Alignment
Burga007 #813891 06/25/20 3:25 am
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The correction to my suggested 'string theory' technique for wheel alignment is a good one - and if I think about it, is probably the way my father used to do it!

The Motion pro tool looks good..for checking sprocket alignment, though I dont think it's worth a tinker's cuss for checking alignment of the front wheel in relation to the rear. I've seen countless bikes on the road where the wheels were clearly not in line (one being our own DB32) though the chain/sprocket alignment was fine..

Just my 2c

KW


No generalisation is wholly true, not even this one.
Oliver Wendell Holmes
Re: Wheel Alignment
JBMorris #813996 06/25/20 9:55 pm
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Originally Posted by JBMorris
"after you adjust tension." - just bought the M/Pro can't wait to get - had to do a new rebuilt caliper recently-'78 Triumph style. . BTW - how do you measure the Chain for tension?

hi JB

what i do is put the bike up on the centre stand, then tighten the chain up enough so i can spin the wheel to find the tightest spot in the chain. once i find it i align the chain using the motion pro tool and then put the bike back down on its wheels, stick a block under the side stand so it stands up straight, and adjust the wheel backwards or forwards evenly until there's about 1 -1/2 inch of total vertical slack in the centre of the bottom run.

this works for my old T120, but machines with the swing arm pivot in a different position relative to the gearbox sprocket might need something less or more. th emanual will say so somewhere.

a little loose is always better than a little tight.


every day you do not take a chance is a day of your life that you will never get back.
Re: Wheel Alignment
Burga007 #814097 06/26/20 6:25 pm
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I agree with Kerry, the chain lining up with g/b sprocket is best for chain wear but when you want it to handle, front and back wheels MUST be in alignment. Don’t be mislead by the chain. I too was shown the string round the rear wheel when I started racing in the 70s and have done it so many times since I can near enough check by eye now without the string.

They just go round corners on rails with the wheels aligned but when out of line, it drops into one side much quicker and hells job to get it over on the other side, depending on which side is pointing the wrong way.

Mal


Daytona Gold Star replica
DBD34/Norton
996 Ducati Boposta
350 MV Augusta
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Re: Wheel Alignment
Burga007 #814114 06/26/20 7:36 pm
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well, i think that wheel alignment and chain alignment are separate problems and should be looked at separately.

you might not fix a misaligned chain by aligning the wheels, and you might not fix misaligned wheels by aligning the chain.

lots of our machines have all been crashed twenty times and repaired with mismatched parts by the time we get them. you have to deal with what you have.


every day you do not take a chance is a day of your life that you will never get back.
Re: Wheel Alignment
Burga007 #814145 06/27/20 12:52 am
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K- Thanks for the help on this one - my instinct says the factory set up the chain to align to the drive sprocket just as M/Pro indicates- restoring innate alignment- ?

My last shade tree method used the brake pads in compression while nipping up the spindle- "will see how that worked out soon .


1978 Bonneville T140V PX
Re: Wheel Alignment
Burga007 #814231 06/27/20 10:02 pm
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DOPE
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the swingarm in my race bike is bent, and so the wheel is tipped some half-inch out of line to the upper left and lower right. haven't fixed it yet.

but it tracks straight at any speed. the bottom of the rear wheel is out of line with the front, ibut t is still parallel, just offset

there are a number of variables to keep in mind


every day you do not take a chance is a day of your life that you will never get back.
Re: Wheel Alignment
Burga007 #814246 06/28/20 1:34 am
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The DB32 with the bent frame I mentioned above, had the wheels running parallel - just not in the same plane. The steering head was effectively twisted, pushing the front wheel footprint out to the right.

Riding the bike, the symptoms were exactly as Mal M mentioned above - the bike rolled quickly into left handers and felt 'uncomfortable' rolling to the right.


No generalisation is wholly true, not even this one.
Oliver Wendell Holmes
Re: Wheel Alignment
Burga007 #814345 06/28/20 9:17 pm
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DOPE
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kerry, i wonder if gyroscopic precession has an effect.

like i said, my LSR machine has a bent swingarm-- the right side is about 1/4-inch higher than the left. so the rear wheel is centered, and can be aligned straight, with the center of its axle in line with the center of the front axle. but the top of the rear wheel is tipped a half inch left, and the contact patch on the bottom is a half inch to the right.

so the contact patches of the front and rear wheels are parallel in terms of rotation, but are offset a half inch.

this should give a handling quirk like the one you describe, where the machine behaves differentlt in left or right turns, or at least requires a noticeable correction at the bars going straight.

yet the machine tracks perfectly at 135 mph, and is completely stable hands-off at 100 mph.

all i can figure is that the offset is being counterbalanced somehow by wheel rotation.

very odd.


every day you do not take a chance is a day of your life that you will never get back.
Re: Wheel Alignment
Burga007 #814393 06/29/20 3:51 am
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If you have plety of spare floor space you can always do chalk up of the bikes geometry.
To do this you need some long strait edges, a plum bob some sticky spots or masking tape and a means of holding the bike . both wheels on the ground & vertical

So you start by plumbing from each side of both axels to the floor where you put some tape then mark the exact place the plum bobs points to.
Note , ideally this should be done fron the center of the axels .
You then plumb from the middle of the steering stem and mark it
And from the swing arm pivot ( both sides ).
While the bike is upright run the plum bob string over the top of each tyre and allow the bob to go to the floor.
If the wheels are vertical, the string should touch the tyre bith top & bottom without deflection ( you will need to avoid writing cast into the sidewalls )
Do this for both sides of both wheels and again mark the spots where th bob touches the ground.

Now roll the bike away.
Draw a line joining each side of the axels, wheels & swing arm pvot together
The 5 lines should be parallel .
Next draw a perpendicular line fom the swing arm pivot line through the steering stem point.
This line should bisect the wheel lines & be at 90 deg to both axel lines
If the wheel lines are different lengths either side of this line then the wheel is off set to the frame.
If the rear axel & swing arm lines are not parallel then the axel is out of alignment.

This method is very accurate and very few old bikes will come out being dead true or square .
The old motoliner frame straitening jig used this to test the accuracy of the frame.
The newer ones use lasers in place of the plum bobs


Bike Beesa
Trevor

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