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 Post subject: Setting up a TT
PostPosted: Fri Dec 03, 2010 6:29 pm 
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Joined: Sun Nov 07, 2010 10:54 pm
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Location: Brisbane
I am playing about with suspension, swingarm length, ride height, and tyre pressure etc and thought it would be helpfull to a lot of people if some recommended settings could be given as well as what didn't work. Graeme


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 Post subject: Re: Setting up a TT
PostPosted: Fri Dec 03, 2010 10:37 pm 
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Graeme,
The best place to start is with getting your sag set in both the front and rear suspension first as this can affect ride height and swingarm droop. Make sure the wheels are in line with one another. Max McAllister (Traxxion Dynamics) put out a loose leave book a number of years ago called "Suspension For Mortals" which is a very good starting point. Your front free/static sag should be about 20mm (bike standing upright-no rider) and about 35mm with the rider on the bike. The rear should be about 10mm free/static sag and about 30mm with the rider on. If your free/static is way off your springs might not be very close for spring rate. Once sag is set then you can go about setting ride height. My experince has been that a swingarm droop of about 12 degrees works good. Getting the 12 degrees usually means adjusting both the front fork length and the rear shock ride height to get there. Unfortunately some bikes don't has much in the way of adjustment to get the chassis setup. Depending on how far you are willing to go, you can make these bikes really handle. I have relocated steering heads, make custom triple clamps and change the shock mount to get thing to work the way I thought they should. This just a starting point and once your out were you can fully test your setup such as the race track them you need to be willing to try many adjustments and setting. See what works for you and what you don't like. This can be a very time consuming process but can be very rewarding.

Since suspension setup is such a big topic let me know if you have a particular area or issue and I'll give you my 2 cents worth.

Palmer


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 Post subject: Re: Setting up a TT
PostPosted: Sat Dec 04, 2010 10:43 pm 
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Location: Brisbane
Hello Palmer,
Starting from sctatch with setting this TT up to see where the rear grip is dissapearing. (possibly tyres also but that's another matter) The front feels good, but the rear is vague.
Some facts,
"95 SS 750 as the doner, using the SS swingarm. The rear wheel can move back another 37mm if needed.
The present length from swingarm pin to axle is 473mm
748 front end, resprung and valved.
Wilbers TT2 rear shock. With extended longer adjuster, at max extension.
17" wheels from SS, 160 x 60 and 120 x 70.

The static sag is 15mm front and 0mm rear.
The weighted sag is 25mm front and 20mm rear.

The swing arm angle is 7.9 degrees static.
So I assume the ride height at the rear needs to increase, or the front needs to be lowered?

At present the weight is 5kg biased towards the front with the bike weighted.

To get the bikes overall hight close for a start what is the height say from a foot peg to the ground at static ?
(as the footpeg position on the frame should be a constant on all TT2's?) Or the underside of the steering head.
Otherwise I could lower the front when the front is already too low, if you understand.
And the problem is in the rear not being high enough.
So, for a start,
With what you've suggested so for, the rear ride height (by swingarm angle) is too low.

Thanks for your time and advice.
Graeme


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 Post subject: Re: Setting up a TT
PostPosted: Sun Dec 05, 2010 12:46 pm 
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Graeme,
It sounds like you have a good start, but my experience with the newer upside down forks is that they are shorter in lenght then what may have been original to the TT. I like to use Honda Showa conventional fork from either a F3 or F4, CBR600 as they are grenally 31 to 32.5 inches from the axle to the top. On Lon Allen's F1 he had to make custom triple clamps that allowed the fork tubes to slide down about 30mm to gat the front high enough (he runs Ducati 748 forks). Based on you description it sound like the front of the bike has to come up and shortening the swingarm may also help, don't go any longer. The rear spring sound a little on the stiff side, you need to have some free/static sag in the rear to allow it to stay in contact with the track. I personally like to run as soft of spring as I can and use the preload adjuster to get my sags. The springs I run usually have to have 12 to 18mm of preload. The tire size and weight basis sounds good. Let me know if any of this helps.

Palmer


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 Post subject: Re: Setting up a TT
PostPosted: Sun Dec 05, 2010 10:03 pm 
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Joined: Sun Nov 07, 2010 10:54 pm
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Location: Brisbane
Yes it helps, it also throws up a lot of questions.


It would appear that my shock needs to be longer to achieve the 12 degrees of down angle,

Then lower the 748 forks as much as possible to raise the front. This will worsten the swing arm angle issue.

Setting more sag on the rear will also add to the low rear end. Therefore putting more weight on the rear. And slow the steering.


SO, if I raise the front by dropping the forks through the tripple clamps as much as possible, about 15mm.
THEN, raise the rear to get 12 degrees of down angle on the swing arm, and reduce the preload to get 10mm of sag, it should be close????????
Even if it's still lower overall than a stock TT2.

Comments?

I have some work to do.
Regards
Graeme


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 Post subject: Re: Setting up a TT
PostPosted: Mon Dec 06, 2010 9:29 am 
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Graeme,

I would start by raising the front as much as possible (sliding the fork legs down). What worked for me was between 10 and 12 degrees with the bike upright with no rider. This may not be possible with your setup as I'm not sure you can get the front of your bike high enough with the fork and triple clamps you have now.

With the front as high as you can go and the rear shock fully extended what is the fork angle? If you have a bubble protractor or angle finder, with the bike upright on both tires measure the fork angle. Raising the front will hlep the swingarm droop. Regardless of the swingarm droop you will need some free/static sag. Also let me know what the front triple clamp offset is. This would be the measurement from the center of the steer stem to the center of a line going betweet the fork tubes. How long is your rear shock center to center?

Let me know what you find.

Palmer


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 Post subject: Re: Setting up a TT
PostPosted: Mon Dec 06, 2010 11:27 pm 
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Joined: Thu Oct 14, 2010 9:58 pm
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Location: Melbourne, Oz
Hi Graeme

I see you are using the stock SS swingarm, I believe the mounting point for the shock on these swingarms is about 40mm further back than on the Verlicchi TT2 steel swingarm. This of course is to make room for the rear facing exhaust on the later Pantah engines.

I maybe taking rubbish here, but would guess that your Wilbers shock would need to be around 340mm eye to eye to maintain the same geometry.

I have got an Ohlins remote reservoir shock for the bike I am building that is 330mm eye to eye, I am thinking now that it is too short for the 750 Sport swingarm I have and am going to run into similar problems as far as swingarm angle is concerned.

Joe


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 Post subject: Re: Setting up a TT
PostPosted: Tue Dec 07, 2010 3:14 am 
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Joined: Sun Nov 07, 2010 10:54 pm
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Location: Brisbane
Hello Joe, I knew it wasn't just me!
Yes you are correct, when I ordered the shock from Wilbers, they lost the bit about the longer shock and just read the TT2 bit. So the shock was too short. We made an extension to get the rear to sit higher so the engine was level. But,,,,,,,,,,
Anyway Mr Palmer has given me some good advice which I'm working with. I'll measure eye to eye as it is now and post the measurements. So stay tuned.
Graeme


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 Post subject: Re: Setting up a TT
PostPosted: Tue Dec 07, 2010 4:44 am 
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Joined: Sun Nov 07, 2010 10:54 pm
Posts: 425
Location: Brisbane
Hello Palmer,

The triple clamp off set is 34mm.
The shock length is 330mm at full extension.

The fork rake will take a little longer to measure. (the steering head angle is definatly 24 degrees, I know this because I had the raw frame checked in a jig for straight before it was painted)

Graeme


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 Post subject: Re: Setting up a TT
PostPosted: Tue Dec 07, 2010 11:43 pm 
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Joined: Sun Aug 08, 2010 4:37 pm
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Location: Ottawa, Ontario, The Great White North
TT1 wrote:
Hi Graeme

I see you are using the stock SS swingarm, I believe the mounting point for the shock on these swingarms is about 40mm further back than on the Verlicchi TT2 steel swingarm. This of course is to make room for the rear facing exhaust on the later Pantah engines.

I maybe taking rubbish here, but would guess that your Wilbers shock would need to be around 340mm eye to eye to maintain the same geometry.

I have got an Ohlins remote reservoir shock for the bike I am building that is 330mm eye to eye, I am thinking now that it is too short for the 750 Sport swingarm I have and am going to run into similar problems as far as swingarm angle is concerned.

Joe


Joe is right on the money regarding the length with the 900SS SA. I was running that SA with the 853F1 and settled on 335mm.

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