first meeting for LS 914, Racing at the MG Classic meeting, Manfeild Park Options

[returf]

Trust me on this...I had thought I had a mechanical failure earlier this year due to the violence of the vibration on my car. We looked at everything and missed the most basic culprit. I had thrown wheel weights and was out 8 ounces. Mount the outboard weights on the lip and tape. You might be very surprised..I believe I've mentioned this before.

Tony

If the shaking happens primarily under braking, I'd look at your rotors.

Thanks Tony, I will get them re-balanced before next event but did you experience your shaking only under brakes ? It's almost like when the shaking starts the play in the coupler won't control the wheels until i remove my foot off the brake pedal.I'll also replace the coupler with an alluminium coupler and get the rotors running with less run-out. I'll keep you all posted.

[Cracker]

Yes. Mainly only under braking - massive vibration - my rotors were new so it was baffling. A friend mentioned the wheels as a possibility and I thought he was nuts. Smooth as ice after having them balanced - I was shocked. This is not to say it's not something else, or in concert with something else, it would be the number two culprit behind the rotors.

Tony

[JFJ914]

is this coupler shagged?

Don't know if that's your problem, but I wouldn't reuse it.

[stownsen914]

Yes. Mainly only under braking - massive vibration

Interesting ... I lost wheels weights once, and vibration was significant, but I felt it all the time, worse with increasing speed. Easy to check though, so definitely worth doing that ...

[jmill]

is this coupler shagged?

Yes, that's garbage. Tangerine makes a Delrin one.

http://www.tangerineracing.com/otherproducts.htm

That's some crazy shaking. If the coupler doesn't fix it I'd look at your steering rack and how it's supported in the chassis.

[Randal]

Trust me on this...I had thought I had a mechanical failure earlier this year due to the violence of the vibration on my car. We looked at everything and missed the most basic culprit. I had thrown wheel weights and was out 8 ounces. Mount the outboard weights on the lip and tape. You might be very surprised..I believe I've mentioned this before.

Tony

If the shaking happens primarily under braking, I'd look at your rotors.

It is pretty amazing what happens after you throw off a few weights.

Been taping them on ever since Bontempi told me how important it was that they stay on.

And don't forget to clean the rim prior to having it balanced and adding weights.

[returf]

Thanks for all your advice Guys. I'm working through the list of things to change. Done new rear sump, working on relocation of exhaust system to accommodate the sump change, Made new steering coupler, Waiting on new axles from the driveshaft shop and I will get the wheels balanced. Thank you all for your guidance and have a great Christmas
Mike (IMG:style_emoticons/default/santa_smiley.gif)

[ablesnead]

Nice car , will be fun when you get it sorted...I have only seen the one photo of the car , but in that one your wing is mounted too low in the turbulence too be effective as it could be.....

[6freak]

looks like alot of fun...good luck with the front ..id try adjusting toe,seems to me the tires are fighting to see who leads the dance,which causes shake/wobble under braking not vibration, your steering wheels not strait, is that a clue?..if its not vibrating any other time its not unbalance of wheels..did you corner balance and align the car so you have equal weight on front tires..good luck this season ,hope you get it pinned down to a root cause

(IMG:style_emoticons/default/smile.gif)

[returf]

Just a bit of an update on the vibration issue. I seem to have got things under control now. I took your advice and got all the wheels balanced, skimmed the new brake rotors and replaced the steering shaft coupler. Hey presto the shakings gone. Had a meeting yesterday and the car ran well. Three races and three good results. I gave the car 2mm toe in on the rear and 0 at the front and it's transformed it into something that doesn't want to swap ends at the slightest hint of steering input.

[Cracker]

Bravo! FWIW: I have 5mm of total toe-in on the rear; zero at the front. With allot of power, such as you have, the trailing arms can be splayed quite severely causing a very tricky condition to handle. Good to hear solid improvements have been made.

PS: What is your oil temp? How are you cooling it? What is your shift point?

Tony

[returf]

Sorry Tony, I meant to say 2mm toe in each side. You had to ask the tricky questions dont you. I have an oil cooler mounted between the rear inner guard and the new outside guard so it gets plenty of cold air. Yep thats one of the other jobs i have to do ( install a temp sender unit and integrate it into the computer to log). Shift point is 6000 rpm but it's really easy to hit the rev limiter at 6200 as you will see when i upload the latest video. I always yearned for a close ratio box and now i have one ( six speed) theres no holiday from shifting gears haha

[Cracker]

Excellent. I look forward to viewing the latest videos...regarding a modern, close-ratio box - I agree (I have said it is almost like cheating)! Which unit did you install?

T

[returf]

Here you go Tony
https://www.youtube.com/watch?v=uyuEF3JPBh0&t=55s


https://www.youtube.com/watch?v=CHLyq3sItX8

[Cracker]

Very much improved - night and day really! As you get more seat time - it appears you will be able to carry a fair more amount of speed through the twisties. I understand it is easier said than done - first hand experience! (IMG:style_emoticons/default/beerchug.gif)

Tony

[stownsen914]

Big improvement! I'm sure the beast is a blast to drive ...

[returf]

Very much improved - night and day really! As you get more seat time - it appears you will be able to carry a fair more amount of speed through the twisties. I understand it is easier said than done - first hand experience! (IMG:style_emoticons/default/beerchug.gif)

Tony

Yes, seat time will help a lot as will changing the 6 year old second hand Porsche cup slicks for something a bit fresher haha. (IMG:style_emoticons/default/driving.gif)

[porschetub]

While most of you guys are nearer the end of your racing season, we are just beginning down here in New Zealand. I finally managed to get my car to it's first meeting last weekend. A classic meeting that is in it's 31st year of running and right at my local track. Practice went well but i noticed that I still had the wheel shake up front under brakes. Race 1 was going well with a demon start but unfortunately a lower arm on the left front broke and that put me out for the rest of the day. Day two, and another good start and went from grid 18 to 9th before the first corner, gee it's got great acceleration!!! Race three and off to a flyer again but three corners from the chequered flag and an axle broke. But all'n'all a great start to the 914's racing. Here's a video of race three. check out the shaking. Once i get that sorted i'm sure i'll be able to brake a lot later.

https://www.youtube.com/watch?v=C4OPnfSt_Lw

What a beast,interesting mix of cars in that race,is it just an ''all in'' class or just a warm up race.

[returf]

Yes there's a great mix of cars alright. This is what is called "Allcomers" at a classic meeting. Anything that runs slicks and doesn't quite meet the COD (certificate of description) for the classic movement gets to race in this class.