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Post by Steve P5b on Jun 2, 2014 11:44:29 GMT
Not having the correct information in my workshop manual, I wonder if someone could supply details of the front suspension geometry measurements in particular the CASTER angle please.
Thanks, Steve
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Post by enigmas on Jun 2, 2014 12:51:42 GMT
I have some literature which stipulates 1 degree positive. (I presume Steve that your wondering why the high speed handling is so vague if not down right dangerous with this minimal amount of caster!) Some have zero caster! You can space the top wishbone ball joint back a bit and perhaps gain one more degree of caster. This was a factory modification. Unfortunately the fixed design didn't really allow for adjustment of any camber or castor.
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Post by Steve P5b on Jun 2, 2014 14:44:05 GMT
I have some literature which stipulates 1 degree positive. (I presume Steve that your wondering why the high speed handling is so vague if not down right dangerous with this minimal amount of caster!) Some have zero caster! You can space the top wishbone ball joint back a bit and perhaps gain one more degree of caster. This was a factory modification. Unfortunately the fixed design didn't really allow for adjustment of any camber or castor. Thanks for your reply , yes I'm considering increasing positive caster to better straight line steering, wondering if any adjustment is possible. Thinking on moving the bottom arm forward and top wishbone rearwards by adjustment of the bushes and spacing with shims/washers etc. I need to find a way of measuring exactly what the dimension are against what they should be etc. Didn't know it was a factory mod, how was it done exactly? Steve |
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Post by enigmas on Jun 2, 2014 22:41:30 GMT
It was done with spacers (thick washers would do) on the top wishbone. Nothing high tech.
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Post by Steve P5b on Jun 3, 2014 11:40:39 GMT
Thanks for that , but I can't see that's possible
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Post by enigmas on Jun 3, 2014 12:46:46 GMT
It's actually very easy Steve.  Think about this. If you can move the top wishbone ball joint to the rear a bit you'll add some castor. View it this way. Look down at the DS top wishbone (like you were superman and had xray vision!) Place a 1/4" spacer between the right hand (RH) wishbone outer end at the ball joint. Then fit a similar sized spacer at the rear (where the bush is) of the LH top wishbone. Yes, the nut won't go on as far. This mod moved the swivel (ball-joint) back 5.38mm or .212" which gave an increase in caster of approx. 1 degree 2 minutes
This information was made available by Rover in May 1972 under Service Information Vol. No3. With a bit of fettling (grinding) you could probably fit thicker spacers for more caster. |
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Post by Steve P5b on Jun 3, 2014 14:59:20 GMT
Thank you for the information. This mod moved the swivel (ball-joint) back 5.38mm or .212" which gave an increase in caster of approx. 1 degree 2 minutes
Read more: roverp5.proboards.com/thread/8300/front-suspension-geometry#ixzz33aX8YSO8
AH, these are the figures I need, I wonder if you experienced this mod, did one degree make a difference to straight line stability ? |
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Post by enigmas on Jun 4, 2014 2:28:27 GMT
Steve, I' don't do anything by the 'rule' book. I cut, repositioned the parts, then rewelded both top suspensions arms (20 yrs ago) to produce 3 degrees of positive castor. It makes all the difference.
Not that I do it, but I can take my hands off the steering wheel (at speed) and the car will track straight ahead without any twitchiness. The self return from corners is also much improved. The shimming is useful for minor corrections side to side.
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Post by Steve P5b on Jun 12, 2014 17:13:40 GMT
More goings on in the batcave today  [ |
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Post by Steve P5b on Jun 17, 2014 16:38:10 GMT
These could give me 4 degrease caster adjustment, adjustable throughout the range. |
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Post by johnwp5bcoupe on Jun 17, 2014 17:59:28 GMT
How fast are bl**dy going Steve  |
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Post by Deleted on Jun 17, 2014 18:03:08 GMT
How fast do you drive Steve? I used to find some problems on the Crossplies but on the Radials my car is steady in a straight line. I don't try to drive it like a modern car so I don't expect modern stability. Hats off for all the trouble you're going to but I personally couldn't be harrised! |
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Post by Deleted on Jun 17, 2014 18:34:07 GMT
How fast do you drive Steve? I used to find some problems on the Crossplies but on the Radials my car is steady in a straight line. I don't try to drive it like a modern car so I don't expect modern stability. Hats off for all the trouble you're going to but I personally couldn't be harrised! PS, Don't forget to tell the Insurance Company. |
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Post by Steve P5b on Jun 17, 2014 18:37:11 GMT
HAHA I would but there not on my car.
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Post by Deleted on Jun 17, 2014 18:44:06 GMT
HAHA I would but there not on my car. You need to clarify whether you are speaking for yourself or quoting someone else's work or description. Why did you post that if it's not for your car? |
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Post by Steve P5b on Jun 17, 2014 21:28:32 GMT
How fast are bl**dy going Steve Not very much at present as having made a device to measure the caster and finding one degree negative I think I realise why the steering is a bit twitchy. This little gadget fits in the centres of the top and bottom joints , the top of the Perspex is compared with the horizontal to find the caster angle.   Moving the top joint rearwards give an indication of caster angle change, one degree = 6mm approx. Hope this is interesting to others. Steve |
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Post by enigmas on Jun 17, 2014 23:07:03 GMT
Good work Steve.  P5Bs are twitchy and scary at the best of times (at speed) on whatever tyres you use. Nil to one degree of castor won't make any vehicle track straight ahead at speed. Also having the steering get lighter and lighter and less directional as speed increases tends to freak me out. Perhaps Tazio Nuvolari could deal with it, but it's not for me. As an aside, many sports cars (e.g. MGB) and many American muscle cars had as much as 6 degrees castor. Having negligible or no castor makes for light steering in heavy cars with manual steering boxes, but with power steering it's superfluous, as any increase in steering load due to increased caster is easily compensated for by the power assistance. Take a look at the front wheels on any Mercedes whilst turning and you'll see evidence of a big castor angle. The transformation in straight line stability is a revelation once it's been experienced in a P5B. PS. That's a clever device. I'll have to 'knock-up' one myself. |
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Post by johnwp5bcoupe on Jun 18, 2014 5:19:15 GMT
It's a great exercise Steve  having built chassis with adjustable Camber and Castor I know it works You still haven't answered my question  how fast are you going to go? or are you doing the Timed 1/4 mile? To be fair the P5b at the speeds we are "allowed" to go and can do in today's traffic the handling is fine for me Being a bit of a nosy Shed engineer how did you arrive at the known Datum Point Steve? I can see how you angle finder works but the chassis would have to be 100% level in both directions and both sides checked for comparison to rule out any funnies on the steering and chassis. If you are doing each side and increasing the castor using the original caster as a reference that works for me as long as both sides work out the same? An interesting project Steve keep the posts coming |
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Post by enigmas on Jun 18, 2014 6:33:05 GMT
A PM to Steve might be the way to go John.
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Post by Deleted on Jun 18, 2014 9:55:10 GMT
It's a great exercise Steve having built chassis with adjustable Camber and Castor I know it works You still haven't answered my question how fast are you going to go? or are you doing the Timed 1/4 mile? To be fair the P5b at the speeds we are "allowed" to go and can do in today's traffic the handling is fine for me Being a bit of a nosy Shed engineer how did you arrive at the known Datum Point Steve? I can see how you angle finder works but the chassis would have to be 100% level in both directions and both sides checked for comparison to rule out any funnies on the steering and chassis. If you are doing each side and increasing the castor using the original caster as a reference that works for me as long as both sides work out the same? An interesting project Steve keep the posts coming John's para 3 sums up P5b motoring for most of us. I don't see a problem unless you are trying to drive your car as if it's a BMW or an Audi or more or less ANY modern car. There are some clever skilled engineering guys on here and I wish someone could have made a decent rear spring shackle replacement to replace the existing arrangement which was fine when new with quality metalastic rubber and good spring camber. |
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Post by Steve P5b on Jun 18, 2014 13:11:43 GMT
[quote author=" johnwp5bcoupe" Being a bit of a nosy Shed engineer how did you arrive at the known Datum Point Steve? An interesting project Steve keep the posts coming [/quote] Ok to measure the caster angle it's crucial to have the car at it's normal ride height and on level ground. Placing blocks under the wheel hub so the centre is at the same height, just without the wheel fitted. I placed a vertical timber block 10x2 with A4 sheet of paper pinned to it behind the Perspex gadget. On this sheet I drew a horizontal line, and also on the top of Perspex gadget, the difference between the two line is measured of with a digital angle finder. Example picture  As you may have noticed the top ball joint has extended studs both sides, so it is possible to fabricate a new rear upper wishbone half with a design to facilitate the upper ball joint to be moved towards the rear of the car and spaced between the front wishbone and ball joint. As it turned out a maximum 25mm spacer still keeps the original extended stud in the plane of shear with the original front wishbone half . A 25mm spacer is the maximum I would use as anything longer would be reliant on the sleeve nut holding things together and as this turns out gives me 3 degrees positive caster starting from 1 degree negative? Three degrees positive isn't excessive as "Vince" suggest. My only concern is the bottom ball joint having sufficient movement to accommodate the top joints new position, until I fit it all up I wont know as the car is still on the road and booked for a few classic car events, amongst other things. |
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Post by johnwp5bcoupe on Jun 18, 2014 15:36:14 GMT
All understood Steve the datum reference I suppose is not critical as long as the chassis is level cross ways and wheel centers equal at the correct height, you are then using what ever datum you have and using that, increasing by ? degrees it should work I would hope the bottom ball joint will cope with the angle? time will tell if it proves reliable? Keep us up to date |
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Post by enigmas on Jun 18, 2014 23:46:19 GMT
Hi John, I spoke to Steve about this mod before he started. 3 degrees is standard for many larger Aussie Fords from the 1960s through to the 80s. These cars have a similar steering layout and this is why l settled on 3 degrees. I modified my top wishbones in a similar manner 20 years ago and the car was used as my primary form of transport until recently. It's probably circumnavigated the odometer at least once since then. The ball joints easily accomodate the angle change..which is negligible if you visualize it.
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Post by johnwp5bcoupe on Jun 19, 2014 6:16:42 GMT
Hi John, I spoke to Steve about this mod before he started. 3 degrees is standard for many larger Aussie Fords from the 1960s through to the 80s. These cars have a similar steering layout and this is why l settled on 3 degrees. I modified my top wishbones in a similar manner 20 years ago and the car was used as my primary form of transport until recently. It's probably circumnavigated the odometer at least once since then. The ball joints easily accomodate the angle change..which is negligible if you visualize it. Tried and tested can't get much better than that vince I did realise how small the off set was and thought the ball joint would be ok but it's Steves project and he is doing fine and if your advising he has a good mentor As I said we haven't the need for speed (too many cameras and Traffic cars not to mention traffic)or the roads to do it in the UK  and at 70-80 I find the handling fine on Radials. |
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Post by enigmas on Jun 19, 2014 8:49:11 GMT
Many years ago I drove a club members P5B sedan John. I'd never driven one before so I had no point of reference. It was one of the scariest experiences I've had in a 'roadworthy' vehicle due to its twitchiness and over-light steering. Another club member told me of his experiences in his well used P5B sedan when he drove it from Victoria to Western Australia and back. His issues had more to do with the concentration required to keep it on a straight line for the extended hours of driving it takes to get to the West coast of Australia. (The distances point to point in this country are extreme. Driving from Victoria where I live, to Sydney...a short drive in relation to going to Western Australia takes 12 hours at legal highway speeds)
I've probably driven half a dozen P5Bs since, some standard and some modified. Ambling around the burbs at moderate speeds is easy and not an issue in these cars. It's when you get on the freeways and drive at (legal highway) speed for extended periods that the poor stability is high lighted. it also creates a lot of fatigue constantly correcting the cars course. Try adding some caster, you'll like it and you certainly have the requisite skills.
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Think about this. If you can move the top wishbone ball joint to the rear a bit you'll add some castor. 
P5Bs are twitchy and scary at the best of times (at speed) on whatever tyres you use. Nil to one degree of castor won't make any vehicle track straight ahead at speed. Also having the steering get lighter and lighter and less directional as speed increases tends to freak me out. Perhaps Tazio Nuvolari could deal with it, but it's not for me.
having built chassis with adjustable Camber and Castor I know it works 
how fast are you going to go? or are you doing the Timed 1/4 mile?
and at 70-80 I find the handling fine on Radials.