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Discussion Starter #1
Are there any upreated driveshafts available for the pg1 gearbox for a zr?

I have broken too many shafts and cv joints now and i need to resolve the problem i have.

The car is a 160 rally car with 2 degrees camber and polybushed around the front end, the suspension has around 6-7" travel at a guess, and sits quite high.

I am running a gripper diff on a very low preload.


I have shortened the std short shaft 6mm as the plunge was about 5mm beforehand, even with the shortened shaft the cv joints mostly fail on this side only and when on right hand tight hairpins.

Any guidence will be appreciated.... and NO i wont drive slower a more sensibly... its a rally not a drive to tesco! lol.

MILO
 

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Discussion Starter #2
Ok, nearly a week and no reply, im trying to source some bigger cv joints that will fit the zr hub with minimal modification, and will be getting shafts made shorter to suit the cv joints.

Not having much experience with most other mg models, i was wondering if the zs/zt cv joints are identical to the zr or larger?

Shortest rally i have ever done!!!

http://www.youtube.com/watch?v=bWTpvC9NKTg
 

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Discussion Starter #3
Ok, just removed the shaft and it has snapped clean off at the end of the splines where it locates in to the cv joint and also the cv joint is destroyed.
 

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From memory diesel shafts and joints are a bit beefier than the petrol ones...?
Not 100% sure though.
Rallymatt would be the guy to ask as he has rallyed ZR for ages.
 

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Discussion Starter #5
Thanks, i shall look in to it.

Im thinking.... Did the factory groupN cars use the bog standard shafts or were they "groupN" ie Modified?
 

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pretty sure that Matt looked at the derv ones, but they are not a direct fit for the petrol models iirc

I seem to remember that the 160 driveshafts were NLA for a while, as Matt picked up the last ones i think.....

best to pm\email\call him as i he really will be the best person to ask about it.
 

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Discussion Starter #7
From a conversation i had a few months ago with a guy i know, i was told that the derv shafts are a different length?? same gearbox though, maybe its to do with the length of the derv engine and that it sits more to one side than a kseries???
 

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It is easy to see from your video , that your first problem is your Diff is not having a gripp almost at all.
In Gripper diff there MUST ( not should) be preload from 90 to 120 Nm. And you must test it after every rally. Driving without enough preload is causing expensive service, and your stage times are going to be poor.

When diff don`t have right amount of preload it will come moore loose very soon, and torque start hammering planet gears, gross pins and planet drivers.
I bet ten beers that there is also a need for some friction plates and also a pair of new preload belleville springs. Remember to ask the latest specification.

Your suspension travel is not the problem. It is not too long. Std driveshafts and joints will survive 8,5" suspension travel is assembled as should. Without any modification.
Set front end height so that when on wheels, both drive shafts are in horizontal position. Adjust rear end about 5-8 mm higher. Test rear height on stage before next event.

Rally Matt, I and some other who are still driving ZR are using std drive shafts and OE joints. S & R did sell grp N uprated shafts which were made from "stronger " steel. They were too stiff and snapped sooner than OE one did.

It is possible to manufacture shafts from our dog box axle steel and they will last "almost for ever" for near reasonable cost. Rally Matt did ask about doing a serie when he was in here during Neste Rally Finland, but we want someone to pay half of the batch of 20 pieces before CNC machine is started. Otherwise it might happen that I will have 20 expensive spare driveshafts which I don`t really need. I`m still using the same shafts what was in the car when I started 6 years ago.

One thing I cant quite follow. Have you really shortened LHD shaft by 6 mm?
Why is that. Whats the point doing it??
How much castor there might be in your car.
Your tyres were not offering a stunning grip so there must be something wrong in basic idea or assembly. Ok you hit the inside wall but in normal case that shouldn`t cause any harm for driveshafts.
 

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Discussion Starter #9
The preload was set at 80nm with the new larger cross pins fitted, it makes
it more driveable in the tight bumpy lanes on road rallies also. Previously the preload was set at 120nm and would pull from side to side and make it very hard to keep straight.

I cant understand myself that the oe shafts are giving up, i was originally breaking the cv joints and after a lot of thought and measureing i found that there was more plunge on the driver side shaft 11mm as opposed to the passenger side 6mm, subframe and shell are not bent whatsoever, i had the clip groves re ground 6mm in and the original clip ring groove was cut straight through, giving a 6mm shorter shaft and a plunge depth of 12mm.

To be honest with you the end of year stage event was just a day out to have some fun and i was useing some very worn Yokohama ao35, the surface was very greasy and muddy in places so not much grip and a lot of sideways fun.:oops:

As for car set up, front tie bars are polybushed and the lower arms, i am not running an anti roll bar.
The tracking is set at 1.5mm toe out, there are a pair of top adjustable suspension mounts fitted, and are set at roughly 1-2 degrees of camber with the top nut closer to the bulkhead, probably increaseing castor, but this has not been measured.

If there is anything i am doing wrong or what i can do to solve this, i am all ears, your advice has helped me a lot so far.:thumbup:
Thanks
 

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Not much time now to think it in English. But a quick one; IF your Gripper dont have any pot holes on ramps and gross pins are perfectly round the Diff is not capable to pull your car from side to side. I have tested GRipper so many times that I can say 80Nm is the lowest possible preload for rallying. I wouldn`t let it so low.

I`m 100 %... no 127,85 % sure that pulling comes from unwanted clearance in suspension and / or wrong position of the wheel. Check at first wheel bearings, lower arm joint and bushing. Any bend parts in suspension or the body? ZR will break quite easily places where steering and lower arm are connected. In one car of Rally Matt we had to spend a day welding chassis rails before the car was driveable for MG Live.

I will be back later to day with some pictures......I hope.
 

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Discussion Starter #11
Thank you, shell and subframe are pretty fresh, i reshelled the car 3 events ago, last october. chassis rails are fully seam welded engine bay side and under the arches.

The engine mount steady bars are polybushed and the gearbox mounting has the polybush inserts fitted.
 

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Ok, just removed the shaft and it has snapped clean off at the end of the splines where it locates in to the cv joint and also the cv joint is destroyed.
I did exactly the same thing to my 200vi at Santa Pod on a launch.

The diesel PG1 shafts are same as the ZR160 I think. RallyMatt replaced my shaft and told me he normally just twists the shafts in his rally experience cars like a cough candy!

I have a pair of diesel driveshafts which came out of a scrappy Rover 220 SDi which I will not be needing. I could sell them to you if you want.

They may need refurbing or something cos they are in "as removed" condition.
 

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First about LSD. If there is right amount preload it is allways possible to drive steadily out of the stage with just one driveshaft.With steady power...

Driveshaft angles and also lenghts are different on LH and RH side. LH shaft is about 400 mm long from joint to joint. In my car when suspension is out the angle of LH shaft is 30 degr. from horizontal. This will cause near 13 mm movement in the axle. RH shaft angle is only 15 degr. because the lenght is near douple, about 700 mm. So free movement is needed a lot less.

That is why also in your car or in any front wheel car there are a lot of free movement because the lenght from joint to joint will vary during suspension movement.

Now when you shortened LH axle lenght by cutting , let me quess; a sharp 90 degr. angle groove , when suspension is collapsing or dropping out to full lenght all stress is in the driveshaft ( in the clip groove). It should be in McPherson and lower arm. No wonder that it does snap when your suspension travel is near the limit on LH side.

How to find out if driveshat is limiting suspension travel. Lift front end up. LH wheel off and also driveshaft nut. When suspension is in full lenght out you should be able to move driveshaft in and out a little. I use as a safety minimum 0,7-0,8mm free play.

If there is not free movement your driveshaft is limiting suspension travel. Can`t be so. Without spring it is easy to lift suspension to see which is the lowest point you can go before driveshaft has done all its free play.
In ZR having normal height , std suspension fixing points and std lower arms also std driveshaft lenght is the one to use.

I include some, not so clear pictures about what happens in Gripper diff if there is not preload enough, but the driver is still pushing. Gross pin is not round anymore, planet gear theets are worn out etc. This Astra did not do more than 20 miles without necessary preload.
 

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The Diesel shafts are different lengths to the ZR160 ones, I have done a lot of research on all MGR shafts and got samples in, measured etc etc.

There are NO driveshafts availble new for PG1 gearbox MGZR or Rover 25.

However we can offer new drive shaft axles with a lifetime (yes lifetime!) warranty for MG ZR with PG1 gearbox.

The axles are made from S155 steel, which is very very strong but has a controlled amount of flex in it to make it perfect for high torque oad applications. Its the same material that Airbus A380/ Boeing 747 landing gear is made from! £250 per shaft plus VAT

Our suppliers will replace any axle that breaks (except impact damage) FOC

Currently lead time is 3 weeks

In addition to the shafts being manufactured from an uprated material, the shaft design is improved to prevent the twisting action that occurs at the shoulder where the splines are cut onto the shaft, by applying a radius rather than a square cut shoulder. OE joints simply fit as per a std shaft.

We can also supply different length shafts for wide track cars.

Effectively you should never have to buy another driveshaft again!
 

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Discussion Starter #15
Thanks for the info snowy, i will pull the diff out and change the preload.

I will also lower the car in the front to get 30 degrees on the driveshaft angle and try it on my next rally this weekend. I have 6mm of movement in the shaft on the passenger side.

Matt, that sounds right up my street, im looking for an uprated short shaft 6mm shorter than standard if thats possable, would really like some contact details please.

Thanks guys :yup:

MILO
 

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Dont rule out fitting Diesel CV joints with BIG FAT shafts....

I fitted special GKN shafts with Diesel joints to my rally car last year, the CV joints are much bigger than the Petrol items and the bars are a lot thicker. If you got Matt to make you bars that are the diam. of diesel bars, you would have the same as me and the problems would go away.

You have to mod the Diesel CV joints to fit, but its worth it to get the larger diam, bars and joints.
 

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I knew exactly what I was going to see before I watched your video, and I was right - 1st gear, full (or near full) lock, full revs.

The first tarmac championship I ever did, we broke four shaft in three events. Causes :-
1. Impact with tyre chicane whilst in 1st gear at full throttle
2. Full lock and full revs in 1st gear (same event, trophy rally)
3. Full lock and full revs in 1st gear.
4. Full lock and full revs in 1st gear.

See the pattern? I changed my driving style after that, and have never snapped a shaft since :)

I know you say you arent going to change your driving style Milo, but it would help - be slightly more considerate to your driveshafts, and they'll get you to the end of the event :racer: :getcoat:
 

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Hi InertiaM, now when you said it I can agree without being the bad boy.

How you drive has a lot influence how your racing vehicle will stand all the stress.I have raced on gravel and snow mainly, but also on tarmac so many hundread laps that I share your point. Most driveshafts are snapped after violent use of revs and ...clutch on starting line. In first gear there is 6 times more torque on wheels than in fifth gear. English Micky Mouse stages do offer millions of places where to distroy the rally car. I have been on Carfax Rally twice , so have some experience aboit that too. If there is any gripp......

In here but also in bumby English tarmac another point where is so easy to distroy joints or shafts are landing after sudden jump or bump. Wheels on air, throttle on we make wheels spinning violently , and when wheels touch tarmac again ....snap. That was common fault during -90`s in 4wd 323.
Every single time when driver landed in third gear throttle on he lost all teeths from 3rd gear. In transmission line there is always the weak link.

If shaft lenght is something which it should not be won`t go long. Std driveshaft is strong enough for most cases, violent use of power is not making us any faster.
 

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Don’t understand much about the type of events you’re taking part but I do understand your driving style is unnecessarily aggressive, from the video your approach into corners looks to be costing you time as you’re having to nail the throttle on exit to gain the momentum you’ve lost, all adds monumental stress to the drive train.
Uprating the drive shafts is going to move the stresses to the next weak point, which will probably be your diff housing.
I race but not the same discipline as you, I’ve broken plenty of drive shafts, diffs and diff housing over the years and learned the change of driving style not only prevented breakages but improved my overall performance and times.
Please don’t take my comments as criticism but advice from one racer to another who’s spent more than enough money on broken parts.
 

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I wouldn't bother using diesel joints, no need as once the axle shafts are up to the job the CV's are more than man enough to cope with what ever a K can give out. Diesel joints are just more weight.

The GKN shafts we found were hopeless, although the stiffer material technically lost less power, they didn't last, they snaped like carrots.

I'm glad Martin put his post in, like Jorma I am not the bad boy of the thread either :))

A word of advice, use much less steering and steer from rear. ZR is such a fantastically well balanced chassis you can make them dance. We also offer tuition, Jorma and show you how to do it on ice too!
 
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