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MG Midget and Sprite Technical More ramblings about recent work and autocross BBS discussion at MG-Cars.net
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MG Midget and Sprite Technical - More ramblings about recent work and autocross
| Hi all, I have been too busy to write much lately. However, I have found the time to do a lot of work and drive my 73 midget. 1) I fixed my burnt wiring (about 10 wires) and installed a new alternator (old one fried). 2) I fixed my bad oil leak (it was not the front seal, it was the timing chain cover). 3) I installed new adjustable Armstrong shocks. One of them was defective (seized) and I am sending it back. The manufacturer is anxious to get it fixed for me. 4) My right anti-sway bar mount got ripped out. I need to beef it up. I did a half XXX attempt at this but now I have to spend the time to do it right. The next race is in only two weeks. I might not have it done in time. 5) I removed my hood mechanism and am now installing hardware on a vinyl tonneau cover. I am happy with the quality and ride height of my new front springs from moss but I don't think that they are stiff enough. I think that they are 380 spring rate (they are not the 400 rate competition springs that they well because the ride height would have been to high). I am not happy with the "stiffer lower" rear springs that I got from moss. What a piece of Chinese junk. One side is higher than the other and one side feels softer than the other. there is no point in adjusting these. I am going to replace them again with stiffer lower (and good quality). I think that I am going to have to go stiffer for autocross. Even with the anti-sway bar and slightly stiffer the car leans too much. I was thinking of trying 500 spring rate in the front. For autocross with a front anti-sway bar what spring rate should I go with in the rear? I am planning on installing a pan hard bar. Also the roll over bar that I am planning is expected to stiffen up the body. Does anyone have recommendations for how the body can be re-enforced as part of this installation (I am pretty sure that SVRA does not permit some kinds of body stiffening design changes but it is ok if it is as a result of the bar installation. If I install 500 spring rate (and adjust my shocks to match) will there be any danger of damaging the car because it was not made to take this much stress? I guess the car weights the same still so perhaps it is ok? The way the lower control arm bolts through sheet metal bothers me and also the fact that the shocks bolt to sheet metal (actually the hole car is pretty much thin sheet metal). I worry that I am gong to start to stretch and bend parts of the car that need to be re-enforced. Has anyone ever done this? Does anyone have any pictures of any changes that they did? I have seen pictures of anti-sway bar mount re-enforcements but if there are any more I would like to see them. Also, if you added any other re-enforcements I would like to hear about it and take pictures. Regarding autocross: Currently my car is pretty slow. I am still using up some lousy Sumotomo all season tires while I do some improvements to the suspension. Two weeks ago I beat a bunch of corvettes but they were novice drivers. They should be able to beat me. Saturday I got last place but all of the drivers were driving hot cars and were very experienced. with the suspension changes that I plan and with better tires I should have been able to beat about 1/3 of the cars I think. However, once the car is really ready I am sure that I will surprise a few people with it. My weight per HP is still pretty bad compared to the other cars but I think that it will be possible to make it equal to a miata after I hop the engine up. I am not going to bother with engine changes until after I am happy with the suspension (suspension much more important I think). sorry I did not take any pictures (kept forgetting my camera). I will next time. Rebecca |
| R Harvey |
| I forgot to add that I ordered one Sparco Sprint 5 to see if it will fit. I am hoping that I can use the stock seat track mechamisms. One more thing. I have new brake calipers from Moss. I am using the high performance brake pads that they sell (the ones that they also mention will make the disks wear quicker). Anyway, I am having trouble with the pads shifting (retainer clips are not strong enough) and after I drive it hard they start to squeak terribly. If I re-seat them (they get kind of cocked) then the problem goes away until the next time I race it. Is it possible that I installed the spacers incorrectly. I can't think of anything else to check. Rebecca |
| R Harvey |
| Rebecca - I've posted some pics of my ARB mount modifications here: http://www.flickr.com/photos/safety_fast/sets/72157623942645649/ Hope that helps! You can view those pictures at full size to see the details... just click the thumbnails, etc. Cheers, and good luck, -:G:- |
| Gryf Ketcherside |
| great pictures. I am assuming that this fix is completely strong enough. Is the new plate 1/8th inch? I was worried that just changing the bottom sheet metal would not be enough. I take it that you don't think that it is necessary to re-enforce the sides? thanks, Rebecca |
| R Harvey |
| Keep the rear soft with something for the sideways location And the front hard (shocks and thick ARB) That should result in a wel handeling spridget and inner frontwheel lift on hard cornering ;) |
| Onno Könemann |
| >>> Is the new plate 1/8th inch? <<< Yes, I believe it is. As for reinforcing the sided, it never occurred to us. We just seam-welded down each edge and across the front. Note that the patch plates are just a bit narrower than then bottom of the chassis rail. The intent was to expose enough of the chassis rail edges to provide a good welding surface. By the way, the photos I posted show the repair to the LH ARB mount, as I'm sure you noticed. We'd done the RH one some time before. I guess we should have done both at once, but the LH one looked okay at the time we repaired the RH side, and we trusted it to hold. Oh well... -:G:- |
| Gryf Ketcherside |
| >>>>>>>>I did a half XXX attempt at this but now I have to spend the time to do it right<<<<<<<< Porn is always hard to get right the 1st time, it just takes practice Rebecca, Its great to see you agian, I was thinking of you the other day. there is a web sight that has some photos of a really nice suspension set up... it will take me a while fid it. But seriously girl, wHat your really in despreate need of is a list of really good suppliers, Moss and Vic Brit, are... Okay, they are better suited for the renovation side then the high performance side of things.... What do you say guys? lets help out rebecca and blow out this thread with lots of high performnce A- series/midget websites ... unfortantly lunch is over and I got to get back to work... but Ill post mine later |
| Prop |
| oh what the heck, here are a couple to start off www.spridget.com Aptfast.com |
| Prop |
| Rebecca, EVERYTHING you buy from Mo$$ you can order from Jeff Zorn at lbcarco.com Same parts 20% cheaper and faster shipping time |
| Phil Burke |
| >>> Rebecca, EVERYTHING you buy from Mo$$ you can order from Jeff Zorn at lbcarco.com Same parts 20% cheaper and faster shipping time <<< And he always throws in a packet of Walker's Shortbreads. Try getting THAT from Moss... ;-) -:G:- |
| Gryf Ketcherside |
| Rebecca, I tried to post yesterday but it seems to have been lost somehow. The 500# springs won't hurt the chassis, but will be really stiff in the front. Two schools of thought on suspension, one is soft springs and large anti sway bars, the other is small anti sway bars and very stiff springs. If you drive the car on the road at all I'd opt for the former and run standard springs and at least a 3/4" or larger front bar. That should be all you need to keep the body roll under control. Most of the racers don't run larger than that. If you want to be able to adjust the ride height you might consider an adjustable spring mount as I made for my car. For the rear springs I used some 1500 rears for the extra spring rate, installed polyurethane spring liners to make the rate more linear, and then used lowering blocks to set the ride height. For serious autocross my front bar (5/8")is a bit small and I get the inside rear tire in the air when I'm really pushing it hard so a larger front bar would help there. Photos of how much body roll I had on the big sweeper which was a bit off camber during the Sprite 50 autocross and of my front spring perch design.  |
| Bill Young |
Spring perch.
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| Bill Young |
| Most of my roll is from my sidewalls. I now run the tyres at 42psi for events. The difference between mine and cars fitted with race rubber is incredible. I am stuck with spoked wheels (original MG motorsport wheels with stronger spokes, and an extra 1/2 inch of width), and no budget for race tyres. And if I had them, I would have no excuses left. |
| Shawn |
| Bill... Thats a cool idea on the ADjustabe spring perch. I like that. Infact, As per My last email heading, if you recall.....AHAhaha hey rebecca, Here is the website I was talking about...if you scroll down he has some great photos of some good suspension moods i think you will like http://www.britishracecar.com/JohnMcCue-MG-Midget.htm |
| Prop |
| >>> Rebecca, EVERYTHING you buy from Mo$$ you can order from Jeff Zorn at lbcarco.com Same parts 20% cheaper and faster shipping time <<< And he always throws in a packet of Walker's Shortbreads. Try getting THAT from Moss...<<<<<<<<<< "Short bread", PHiff!!! British parts north west gives you a hand full of Hard candy and is also really good on pricing www.bpnorthwest.com |
| Prop |
| Shawn, howmany bar is 42psi? |
| Arie de Best |
| Here you go Arie.. http://www.kwik-fit.com/tyre-pressure.asp short answer....( 2.90 = 42psi ) Prop |
| Prop |
| But lets face the truth arie... Isnt this really a cry for help... If your replacing PSI for BARS, maybe this sight is what you really need.... www.aa.org/ hahahaa |
| Prop |
| Prop. That John McCue's car site is real automotive porn. The car looks a million dollars. Trouble is, it probably cost that much. How much money do some guys have? I just hope he gets some good race results with it. Bernie. |
| b higginson |
| Bernie, That car makes me jealous and envous, I cant imagine the money he must have spent... I dont think id ever race it... Infact id make a coffee table out of it... its pure art, or as you and Jessie helms calls it ... PORN what gets me, I had the exact same idea of the ladder bars on the rear axle,(rose heim joint bar under the leaf springs) and I even got most of the parts to make it, at least I know what it looks like in real life |
| Prop |
| Bill Do you have a photo of those spring perches in position ? I have seen these mentioned before but never seen anybody using them, do they work ok ? Ian |
| Ian Webb '73 GAN5 |
| No photo Ian, I made these myself, my own design. They bolt on in place of the original lower spring pans. Here's a drawing of the construction details. To adjust the height you turn the lower nut with a large socket and breaker bar causing the rod to rotate and force the spring mount upwards or downwards. I added some small pieces of steel around the spring mounting plate to keep the spring centered there. I used some one inch threaded rod I bought at the local hardware store, similar stock should be available in your area. Steel flat stock was 3/16" thick. I added some reinforcement around the lower portion of the bottom plate to prevent it from bending under the load. I needed to raise my car a bit to start with so the extra thickness when fully lowered wasn't a problem, but these would space down easily and allow a lower ride height for track days and then easily raise up for the road trip home over the speed bumps.  |
| Bill Young |
| Thanks Bill That's given me some food for thought, I am racking my brains to find the site where I saw another drawing of the same concept 4 or 5 years ago. If I find I'll post it here. Ian |
| Ian Webb '73 GAN5 |
| Bill I have seen a similar set up to yours here: http://www.omniautos.force9.co.uk/sprite/m_frsus.htm Ian |
| Ian Webb '73 GAN5 |
| Ian, That is one radical site... thanks for sharing, I liked the section on stiffing the rear leaf springs...Now that is out there...flipping the 3 lower ones upside down...wow. |
| Prop |
| Prop, That John McCue site is already one of my favorite links. Every time I look at it I notice something new. Rebecca |
| R Harvey |
| Rebecca, as I wait for more input to my gear box thread I look down the thrad list and see this suspensions discussion hopefully, you are still monitoring it! I think one realy important handling trait that hasn't yet been discussed is the ballance front to rear. A car that predominantly oversteers or understeers is not going to be fast. What ever spring rates you do end up with drive the car and if it understeers you need to soften the front roll stiff or stiffen the rear, and coversely if it oversteers you need to stiffen the front or soften the rear. I ran my Sprite MkIII in the Road Going Class of the UK MGCC Speed Championship. We had to use mostly standard suspension components, but were permited to change spring rates. I set my car up with a 11/16ths roll bar(max permitted), 400 lbs front springs, which cut down body roll and dive under braking, but also as I had only stiffened the front also gave me a car that understeered. To make it more neautral I made up some custom rear springs which effectively have an extra 2nd leaf (possibly these extra stiffness rear springs will do similar). This stiffend the rear roll stiffness, and brought the car back into a neutral ballance. In fact the car still has a slight understeer, which under full acceleration in 2nd or 3rd will ballance out the car front to rear or understeer/oversteer perfectly (i.e. on corner exit). If regulations permit you also need to set your car up with approx 1.5 degrees of negative camber on the front (although opinion may vary between 1 to 3 degrees). Do this before you attempt to balance the car as it will aid front grip. Also I agree with the tyre pressure comment if your running high profile tyres the additional carcass and tread stability that's gained from pressures in the region of 40psi, is certainly useful. Run less in the wet as you don't need so much carcass stability as there's less grip available, and a slight bigger contact patch is worth having. When you're competing try to get some good front on pics of the car, and look at the tyre defelction, and the camber of the front wheel on the outside of the corner. This will tell you a surprising amount about body roll, camber and tyres. Good luck with it all, it's great fun and a cool challenge. Remmber you don't need to spend a pile of cash to go fast. James E |
| James Eastwood |
| Rebeccca, Here's some photos of the bugeye we run. This is a old SCCA car that is now run in vintage. I'm not sure where you will eventually go woth your car as far a competition level. If you go into vintage or something like that, a good way to stiffen the chassis is to run a bar up to just behind the fron suspension mounting points. We explain this away as being a "safety issue". I also know where you cold get a set of rear composite springs that are vrey light. A few modifications of the mounting points are required. but it isn't that big of a job. Otherwise, think about some offset springs to accomodate wider tires. http://www.photoshop.com/user/tmichnay/?galleryid=dae72b50b62947d49300f482f4c93648&trackingid=BTAGC&wf=sharegrid&rlang=en_US |
| Tim Michnay |
This thread was discussed between 11/10/2010 and 03/11/2010
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