Can any of you Gentlemen advise me of the factory recommended suspension geometry for these cars, particularly front and rear caster and ackermann angles. Also, if any of you have found better alternative settings I would be very interestyed to know these as well. Thank you, Frank
RF Mk1
- Thread starter wealdenengineer
- Start date
Hi Frank,
you could always ask "the factory" !!??
What are you using the car for ie track vs road, which shocks and springs do you have and which tyres and rims ? I have recently sent info to assist an RF in the UK, not sure if you ar eon the same car ?
Caster on the front ends up being around 6 degrees
if you use all std RF parts including spacers (I'm not so sure about the few South African built cars) . On the rear you may only achieve 2-3 degrees although increasing this will improve handling predictability and toe change per current RF cars. we have retro fit kits but I am not sure which car you are working on nor it's end use ? .
The cars had negligible ackerman and still do - it's a trade off between, amongst numerous other factors, packaging brakes, steering arms and high offset period wheels, kpi, scrub radius, lateral grip and steering feel. Our extensive development over the last 12 months with a bunch of very experienced engineers and drivers showed increasing ackerman had a negative effect on and off the track with our particular component set up - I am not trying to open a can of worms here, and possibly the next 500 posts will tell us why ackerman is so good - in many other applications it is - the current RF car was simply a lot better without much as evidenced by subjective evaluation by several well credentialed drivers and objective measurement including lap timing and steering effort and input. This does not mean we think negligable or even anti ackerman is always the answer - each situation is unique and in other applications there will be advantages and disadvantages.
Enough of my rambling - please feel free to PM details if you would like some more help
Regards Paul
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Paul, my apologies for not going directly to you, and as I thought you have moved on from the early cars, development always improves the breed ! My thoughts on ackermann correspond closely with your own, particularly on the gt40 base plan, so we are at least on some common ground here. I would like to see 8 degrees caster if it is achievable, but wont know until I get in there - can you advise if it is possible. You will be getting another E mail from the owner of this car this weekend asking similar questions for me. thanks for your help, Frank
Hi Frank,
no problem, please always feel free to ask as we've had a bit to do with RF1 as well in fact it was all current production until recently. At 8 degrees of front caster you are likely to see some increased steering effort and given the steering arm is not removeable ie one piece with the upright you will start running into some additional bump steer unless you alter (raise) the rack location. There will be diminishing gains, probably around 8 degrees. On an Aus built RF1 you could achieve your desired 8 degrees within the std pick up bracket using spacers.
I'll look forward to an email, always happy to help and from Huw's last PM it sounds like it has improved a lot over the last week which is a nice result so far.
Hi Jim,
I am having a close look at LHD at present, everything on CAD is finished (to match the characteristics achieved on the local cars) and once the actual rack arrives and we set it up I'll let you know. The change to the front end is quite substantial and includes steering wheel hub, column, intermediate shaft, rack, upper and lower wishbones, new uprights and associated hardware, hubs, rotors, shock mounts and springs. One of the design constraints we set ourselves was to leave the chasssis pick up points per RF1 so that these retro fits will be achieveable, we are nearly done on the local RHD retro fits, the first builds have had the changes for some time. Thanks for your interest, we'll keep you posted,
Regards Paul
no problem, please always feel free to ask as we've had a bit to do with RF1 as well in fact it was all current production until recently. At 8 degrees of front caster you are likely to see some increased steering effort and given the steering arm is not removeable ie one piece with the upright you will start running into some additional bump steer unless you alter (raise) the rack location. There will be diminishing gains, probably around 8 degrees. On an Aus built RF1 you could achieve your desired 8 degrees within the std pick up bracket using spacers.
I'll look forward to an email, always happy to help and from Huw's last PM it sounds like it has improved a lot over the last week which is a nice result so far.
Hi Jim,
I am having a close look at LHD at present, everything on CAD is finished (to match the characteristics achieved on the local cars) and once the actual rack arrives and we set it up I'll let you know. The change to the front end is quite substantial and includes steering wheel hub, column, intermediate shaft, rack, upper and lower wishbones, new uprights and associated hardware, hubs, rotors, shock mounts and springs. One of the design constraints we set ourselves was to leave the chasssis pick up points per RF1 so that these retro fits will be achieveable, we are nearly done on the local RHD retro fits, the first builds have had the changes for some time. Thanks for your interest, we'll keep you posted,
Regards Paul
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Paul, thank you for your very helpfull information, so different from the previous incumbent of the RF name ! Frank
Ross Nicol
GT40s Supporter
Bob
The more front caster you run the more camber gain you get on the outside loaded wheel in a corner. This is a good thing, as the only alternative (if you need more negative camber) is to increase static negative camber, and you can end up with a small inside tyre footprint. Which is not good for straight line braking. The only negative is the resulting steering effort required. This then is overcome with power steering. Last time I spoke with John Bowe he admitted he doesn't like driving cars without power steering. Personally I think I've hit a nice compromise with my car.
Ross:thumbsup:
The more front caster you run the more camber gain you get on the outside loaded wheel in a corner. This is a good thing, as the only alternative (if you need more negative camber) is to increase static negative camber, and you can end up with a small inside tyre footprint. Which is not good for straight line braking. The only negative is the resulting steering effort required. This then is overcome with power steering. Last time I spoke with John Bowe he admitted he doesn't like driving cars without power steering. Personally I think I've hit a nice compromise with my car.
Ross:thumbsup:
Ross, what are your numbers ? Frank
HI Frank,
some of the numbers on Ross' car and the '09 RF cars may not be particularly relevant to you as both use significatly less scrub radius than the RF1 cars. (not to mention Ross' is a race car on slicks !)
There is a compromise between body roll, camber gain, self centering feel and steering weight, you will probably find 5-6 degrees is good middle ground in this application, if anything less would favour steering weight but at the expense of camber gain and the bump curve (verticle rack location, fixed steering arms).
JB's power steer interest is not necessarily about steering effort or weight, it can dampen road input signals (through the steering wheel) especially on harsh bumpy conditions on c grade roads. As Ross is aware he has done a LOT of testing and evaluation for us through a range of conditions on the new set up - another story, another time.
Regards Paul
some of the numbers on Ross' car and the '09 RF cars may not be particularly relevant to you as both use significatly less scrub radius than the RF1 cars. (not to mention Ross' is a race car on slicks !)
There is a compromise between body roll, camber gain, self centering feel and steering weight, you will probably find 5-6 degrees is good middle ground in this application, if anything less would favour steering weight but at the expense of camber gain and the bump curve (verticle rack location, fixed steering arms).
JB's power steer interest is not necessarily about steering effort or weight, it can dampen road input signals (through the steering wheel) especially on harsh bumpy conditions on c grade roads. As Ross is aware he has done a LOT of testing and evaluation for us through a range of conditions on the new set up - another story, another time.
Regards Paul
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Ross Nicol
GT40s Supporter
I'm a bit hazy on what my front caster ended up at. but I recall trying to get it to 7 or 8 degrees but couldn't due to wheel clearance issues at the time. (This was prior to my reduction of scrub radius).I remember I had the caster at 4 deg prior to the SR mods. The changes in scrub radius had such a dramatic affect on the steering kick back and weight (which was my main problem) that I haven't revisited the Caster/camber gain since. My static front camber is 4 deg negative and this gives me very good temps and wear on the slicks.One thing, with the front caster at 4 deg I didn't have to continually correct the steering down the straight and I still had enough self centreing.
I agree with Paul that 5-6 degrees caster would be in the ball park.
Ross:thumbsup:
I agree with Paul that 5-6 degrees caster would be in the ball park.
Ross:thumbsup:
Thanks Ross, I had a long and pleasant conversation with Paul this morning, I think at the end of the day it what suits the car and its particular application that counts, I will let you know what I finish up with, Frank
