Suspension Settings - Dialing Out Bump Steer

[UltimaCH]

Nice to hear you got it sorted right. When I worked of formula cars many many moons ago, dialling out bump steer was very important and something which needed to be checked and adjusted very often.

[Mr Pid]

I spent a day last weekend tinkering with my laser pointer taped to the top of my tyres pointed at the wall while I jacked the suspension up and down. To get everything spot on had to lower the rack about 1or 2 mm both sides. Took some time but very easy. Have ended up pretty well completely eliminating bump steer.

....the results are extremely impressive.... No longer have to 'hang on tight' over bumpy roads and all feels incredibly more relaxed and less likely to bite you. If you have not yet done this I highly recommend doing so as a bit of Winter tinkering...

[GtrMan]

Mr Pid said:

I spent a day last weekend tinkering with my laser pointer taped to the top of my tyres pointed at the wall while I jacked the suspension up and down. To get everything spot on had to lower the rack about 1or 2 mm both sides. Took some time but very easy. Have ended up pretty well completely eliminating bump steer.

....the results are extremely impressive.... No longer have to 'hang on tight' over bumpy roads and all feels incredibly more relaxed and less likely to bite you. If you have not yet done this I highly recommend doing so as a bit of Winter tinkering...

Is there allowance in the chassis holes to move the rack or you had to slot the holes to gain the 1 to 2mm for adjustment.

Tks.....Mark

[Mr Pid]

There is no allowance for this in the chassis holes. I started by measuring the bump steer and working out which way I needed to go. I then moved the rack out the way and took a file to the holes to slot them downwards.... Gave myself about 5mm to play. To do this needed to remove the battery and also needed to use a very short file for the lower bolts so I didn't need to remove the rad. Then bolted things back up loosely and moved the rack down till bump steer was removed.... Then retorque bolts when all set.

[GtrMan]

Very interesting info ... so what determines exactly if to go down or up with the rack to avoid slotting both ways.

Many thanks ...Mark

[Mr Pid]

Google will help you...... But basically for an ultima if you get toe out with compression / toe in with rebound then you need to lower the rack... This is what I had to do on both sides.

[Storer]

It would be really helpful if the Factory (please take note Richard) would slot the holes for the rack during production, as most cars seem to need some adjustment. We all hate to file through the powder coat!!!

Paul


BTW.
I wish I had slotted mine before powder coating after rebuild!!!!

[ezakimak]

spatz said:

so looking at the left wheel with a bump and toe out the car tends then to turn left, and with
toe in tends to turn right ? Is that what you mean with toe in and out ?

thanks

yes, if the left wheel moves up, and you get toe out when this occours , then the car would pull to the left
if you were getting the car pull to the right i would suspect you had toe in.

[5paulmv]

May be a daft question but do you set tracking and camber etc before or after doing bump steer or set everything else first . As I intend checking this over winter cheers Paul

[JohnMcL]

1. Camber
2. Castor
3. Toe
4. Bump.

Also - why file slots for the rack when you can use washers at the steering arm connection?

[spatz]

JohnMcL said:

1. Camber
2. Castor
3. Toe
4. Bump.

Also - why file slots for the rack when you can use washers at the steering arm connection?

Hi very interested in your way of doing it !

are you familiar with the ultima rack ?
the steering rod is multitooth with a securing bolt and IMO no way to use washers to adjust anything ?
correct me if wrong but of course sollting the chassis is much harder than using some washers

[JohnMcL]

You mean you Ultima folk don't have proper adjusters - like this

Tough - so its back to filing slots

[deadscoob]

There are plenty of bump steer kits available for cars, surely something similar can be made up to stop the phaffing around filing slots in the chassis?

[UltimaCH]

I've been reading through this thread, but is there no other way to correct bump steer except filing slots in the steering rack holes. As others have posted and said, I'm not 100% at ease with this solution.

[Mr Pid]

You need to adjust the effective arc of travel of the track rod..... assuming you are not going to change the rack itself, that means adjusting either the height of the inner end of the track rod (ie rack)or the height of the outer end of the track rod (ie steering arm). The steering arm end on a regular Ultima is not adjustable.... although as seen above other set ups can offer this.

[Mr Pid]

..... and phaffing and phettling are part of the phun my phriend !

[UltimaCH]

[356Speedster]

Just to bring this thread back upto date....

I've not driven the car much since my last update and while the car does feel a lot better, because I used the laser pen method, I want to be fully confident in the car's BS geo. As such, I'd like to get people's feedback to the Longacre 79000 Bump Steer gauge..... I've got an option on getting a new one shipped to the UK for £130 (I could probably sell it on when I'm finished with it for no loss, as they tend to be well over £200 here). Has anyone used one before? Any feedback on it's ease of use? It seems to be the default gauge for the job, so I think it should be a decent investment and the best way I'll know for sure what the car's setup is.

[Justaredbadge]

356Speedster said:

Just to bring this thread back upto date....

I've not driven the car much since my last update and while the car does feel a lot better, because I used the laser pen method, I want to be fully confident in the car's BS geo. As such, I'd like to get people's feedback to the Longacre 79000 Bump Steer gauge..... I've got an option on getting a new one shipped to the UK for £130 (I could probably sell it on when I'm finished with it for no loss, as they tend to be well over £200 here). Has anyone used one before? Any feedback on it's ease of use? It seems to be the default gauge for the job, so I think it should be a decent investment and the best way I'll know for sure what the car's setup is.

on race cars with similar suspension we used to do it with the same string set as for setting the tracking. just disconnect the damper/pushrod and measure the toe at different heights throughout the travel.

[UltimaCH]

Justaredbadge said:

on race cars with similar suspension we used to do it with the same string set as for setting the tracking. just disconnect the damper/pushrod and measure the toe at different heights throughout the travel.

Correct, but on race cars it is much easier as you play around with the suspension rose joints. This becomes a bit more challenging with non moving nylon bushes!