Steering, Suspension, & Brakes

Hi all, I have bought the Hoyle Front suspension, pre owned and without coilovers and springs.I'm getting conflicting information regarding eye to eye dimensions for the coilovers. Can anyone help with the correct open and closed dimensions?

Larry Shimp has the Hoyle suspension. He isn't very active on the board, but I think if you PM him he'll get an email alerting that there's a new PM to read. That's probably the best way to reach him.

Larry's handle is 302GT

Thanks guys as usual you spend ages looking for info before posting this thread and then today I have found the dealer who supplies the coilovers for the Hoyle kit.

I found the Hoyle springs to be way too stiff, and the Spax shocks to have deficiencies in damping - the single adjustment stiffens both rebound and compression at the same time; best set up is soft compression and stiff rebound. I am using QA-1 shocks; the factory compression rate is fine, and the single adjustment only affects the rebound. The Hoyle springs are 2.25 inches in diameter while most coil over springs are 2.50 inches in diameter. 2.5 inch springs might fit if they are of the strength I like; 200 pounds/inch (I believe Hoyle springs are 300 pounds/inch). With the very stiff springs, the shock rebound setting needed to also be very stiff and with the correspondingly stiffer compression with the Spax shocks the suspension was almost immovable. If you are interested, I can look up the exact shocks and springs I used; but it may take a few days.

Note; I bought the suspension years ago and there might have been upgrades since then....

Hi Larry,
I also have the Hoyle front suspension but haven't installed it yet. Didn't know about the problems you had. What type of QA shocks and springs did you use ?
Still working on the body rust. Door sills and rear fenders.
Werner

I could not find my old SPAX shocks to measure, but I think you want the QA1 shocks with 11.1 inch extended and 8.6 inch compressed dimensions. The compressed dimension is the most critical. As I recall, the poly bushings fit the Hoyle mounting bolts (if not, bushings are available). The QA1 bushings hold up well, the SPAX bushings only last a few hundred miles (at least that was true when I had them years ago). The shocks are set up for 2 1/2 inch springs but 2 1/4 inch springs will fit. It is possible that small spring diameter wire 2 1/2 inch springs will work, but I used 2 1/4 inch springs on mine. The shocks can be bought from many places such as Summit Racing; the springs are much rarer but are available from Pegasus Auto Racing, length is maybe 10 inches (or possibly 8 inches?). Again, I recommend 200 pounds/inch spring rate; this is fine for a Ford 302 in an MGB GT.

Thanks for the information Larry, but I had already ordered the coilovers. I have checked your car out and what an impressive work of art it is.
Can you please provide more information regarding your setup, in particular spring frequencies in cycles per minute.
I decided to modify the Jaguar IRS to fit my kit car and after feeding all the parameters into my suspension program I came up with 4x160 lbs" for the rear and 250 lbs" for the front. This gives me 109 cpm rear and 93 at the front, your 200 lbs" springs according to my calculations give 83 cpm and a little to soft front to rear for mine.

I have not calculated the suspension frequency, but I will look into it it.The Hoyle suspension system uses equal strength springs at all four corners and my car is within a few pounds of a 50/50 weight distribution (like a stock MGB GT), 1240 lbs front 1208 lbs rear with a nearly empty gas tank, so I kept the springs about equal when I changed them (200 pounds front, 225 rear; the rear tended to squat too much under acceleration with 200 pound springs). The 200 pound springs do not seem to be too soft; the suspension never bottoms and brake dive is minimal. However, setting the shocks to a very soft setting does not work well, but that is to be expected.

I have a rear sway bar (as well as a front bar) and that is very important; oversteer is very controllable with the rear bar, and not so controllable without it (I have never spun out on a road course as long as the rear bar is connected). I originally built the car when I lived in NJ and the roads there are in poor condition. With the stock springs, the car just jumped sideways on corners as the tires bounced off of the bumps in the pavement. With the softer suspension, road holding was far better. Note: Hoyle has the philosophy that sway bars should not be needed, it is best to just make the suspension stiffer. This may work on smooth pavement, but not where I drive. I am using a 3/4" front sway bar and a modified stock 9/16" Midget front bar on the rear (the arms have been shortened so the rate is higher than stock).

Mel, perhaps you can calculate my spring frequency; you already have all of the suspension measurements and I supplied the front end weight of my car (1240 lbs). That saves me the effort of going out in the cold and measuring the suspension dimensions and shock angle...

Surely its not COLD in Minnesota. Probably SNOW also :-). Stay Warm and hope to see you in Dayton.

No problem Larry, As i'm sure you are aware there is a difference regarding unsprung weight. I have a friend with the same car as mine but his unsprung weight is 24 lbs more per corner due to his 100 spoke wire wheels. My CPM at the front are 93.48 his 88.44 with the same 250lbs springs. My 3 piece Compomotive 15x6 wheel and tyre is 36 lbs so when it warms up there weigh yours, my thinking is yours are lighter and will put the CPM up. Your 200 lbs" spring give a wheel rate of 101.10 and CPM of 81.41. I hope this is helpful.

Does CPM have any relation to sensitivity to wheel balance? I realize that the spring CPM frequency is much lower than the wheel rotation speed but there could be harmonic interactions. Anyway, the only way for me to get a decent balance at speeds above about 60 mph is to go to road force balancing. Probably a bigger factor is unsprung weight, the larger it is, the more sensitive the car is to wheel balance, but maybe there is more...

I don’t know Larry but the lower the CPM the softer you will be setting damping too, conversely the higher the CPM wouldn’t imbalance need to be higher to show up?
As road force balancing works for you, do you think it could be down to uneven tyre deflection also possibly side to side or front to rear?

I believe lower tire pressure makes the car less sensitive to imbalance. I plan to experiment, but it is still cold here, lows around 13 degrees and more snow is expected. Supposedly a warming trend next week....

Hi Mel,
Do you still need the Hoyle dimensions ? I came across your thread . I also have the Hoyle front suspension. Had it for 8 years stored in boxes in my garage. Bought it direct from Hoyle when I was working in the UK.
Just now I have the front crossmember bolted to the body. Looks good . I lost the instructions on how to install and fine tune it. I might have some more questions when the car sits on its 4 wheels.

Werner