vibration between 70 - 75 mph

Post by **KirstMin** » Tue Dec 06, 2005 1:35 pm

Now that I can get my car up to these speeds, I seem to have a vibration which lasts between 70 -75 mph (ish). If I pass through the speeds and up to 80 it runs smooth again, and likewise if I drop below these speeds.

Would this likely be wheel balancing or does it sound like something else?

cheers

Post by **Matt** » Tue Dec 06, 2005 1:57 pm

Naughty!!! your not meant to go that fast!!!

Post by **paulk** » Tue Dec 06, 2005 2:15 pm

I am sure Kirstmin was refering to his Indicated speed which he is sure is over reading by at least 10%

I've had similair problems and just driven through it.

Wheels would wobble all the way up to that speed.

It could be a high rev engine wobble or the prop or axle.

If you could work out what equivalent speed in third would be, you could decide whether its engine or drive train

Post by **bigginger** » Tue Dec 06, 2005 2:39 pm

paulk wrote:
Wheels would wobble all the way up to that speed.

Not in my experience - sounds just right for unbalanced wheels to me... Could still be the other things, but I'd have thought getting the wheels done was a good plan.

Post by **KirstMin** » Tue Dec 06, 2005 3:29 pm

Matt wrote:Naughty!!! your not meant to go that fast!!!

Well I'd spent 3 days - engine out and all for a 1275 - changing my camshaft to a fast road one and my cylinder head to a stage 3 one, of course I only went over that speed for a short time, simply to test that the car was safe

.

I'll get the wheels balanced... I have some minilites from JHL and one of the sticky balancing weights fell off when I put them on the car. Those sticky things are RUBBISH!! I don't know which wheel that was on mind.

Like BG, I always thought that badly balanced wheels could give problems at certain (high?) speeds, not all the way up. Somthing about natural frequencies and all. I might be wrong though

Post by **paulk** » Tue Dec 06, 2005 3:50 pm

Well you learn something new every day

I've only ever lost one wheel weight and I knew about that from 40mph up.

Post by **jonathon** » Tue Dec 06, 2005 9:11 pm

Is the vibration through the steering or the drive train?.

Post by **Willie** » Tue Dec 06, 2005 10:13 pm

I would be surprised if it was a wheel balance problem as that would usually
appear at a certain speed and get progressively worse as you went even
faster?

Post by **bigginger** » Tue Dec 06, 2005 10:48 pm

It can do Willie, but I've also found that you can drive through it quite often.

Post by **Onne** » Tue Dec 06, 2005 10:50 pm

Just hit the kerb at exactly the right place.

I did read/see a guy who used a hammer to balance his wheels, so he wouldn't need to use lead.
Real craftmanship that. and a lot of work

Post by **Packedup** » Tue Dec 06, 2005 11:28 pm

In my days of driving fairly nippy repmobiles far too hard (instead of now driving failry sluggish classics far too hard - Less chance of breaking the speed limit in the latter, more chance of breaking the car though) one car I had was a nightmare at about 70mph. Didn't clear up completely till about 105.

Was never quite sure I'd get away with doing three figures on the grounds the car felt better balanced at that sort of speed...

But anyway, yes, quite often you can drive through the vibration to a point of calm the other side

Post by **Willie** » Wed Dec 07, 2005 7:51 am

OH,well I never experienced that phenomenom despite daily driving up the
M1 for many years, perhaps with enough speed the car starts to lift up so
that the out of balance effect is diminished? I would have a hard job to go
fast enough to cure my Minor!

Post by **Peetee** » Wed Dec 07, 2005 11:25 am

I have this on a 1300 minor too (Yikes i don't want to change back thanks

). Having recently refitted the bushes on the front suspension I checked all this and found a small amount of take up on two bolts. The top pivot in particular is very difficult to get right as you are tightening against the bush which may, or may not be located accurately. Anyhow, this didn't completely get rid of the wobble - only making it occur at higher speeds. My best guess is that it is a wheel balance problem. but I have yet to get it checked.

Post by **KirstMin** » Wed Dec 07, 2005 4:24 pm

ok, first port of call is the balancing. I've checked with a tyre place and apparantly unbalanced wheels can be the source of vibration between certain speeds.

Failing that, Jonathan of JHL reckons I might need spigot rings on my hubs because I have minilites and they dont locate fully on the centre hubs. BUT (before everyone jumps in and says how dangerous this is) ... I've checked with some mini specialists and minilites (including the Rover Sportpack wheels) DONT locate on the hub centres either. The recomendation is to do them up carefully, criss-cross style and to exact torque.

I'll let you know if its balancing tomorrow.

Post by **bmcecosse** » Wed Dec 07, 2005 7:12 pm

The wheels DO NOT locate on the hubs - the studs/nuts should centre them up ok. You can check front wheel balance by jacking the car up - and if the wheel is out of (static) balance it will turn until the heavy part is nearest the ground! Disc brake fanatics will need to take the pads out first of course. Then turn the wheel 90 degrees - and add balance weights on the opposite side until the wheel no longer wants to turn. It's a very crude (one might say gung-ho!) method of balancing the wheels - and it is only a static balance, not dynamic - but it's free, and it works very well for my car - no trace of tremor even well round the clock. this method has the advantage of taking the out-of-balance brake drum into account (n/a for discs) - but then it is important to mark the wheel and drum so they will be re-fitted in the same location. Rear wheels need to be brought forward for balancing and then sent back again. A refinement I haven't used would be to simply fix a spare front hub into the vice - and do it there !

Post by **Willie** » Wed Dec 07, 2005 7:47 pm

Yes, this is a worthwhile excercise which I did(to check why my professionally
balanced front wheel persisted in stopping in the same place each time). It
resulted in my removing the wheel and finding that the brake drum always
stopped in the same place which was only cured when I ground some of the
metal from the rim of the drum!

Post by **jonathon** » Wed Dec 07, 2005 8:20 pm

Despite BM's shouting, I would still recommend that alloys be located via the center bore and only tightened into a final position by the studs. Apart from the obvious fact that a centrally located wheel cannot stray from its correct position, we should consider the fact that the wheels in question are based on Minorl PCD and Ital centerbore. The wheel studs have atleast 4mm clearance in diameter on the wheels stud bore, even allowing for a 60% taper on the studs the wheels will have the potential to move, if not centrally located as there is atleast 25-30mm of unsupported stud. If the wheel were a steel one then the face of the wheel is in comlpete contact with the drum and there will be no distance of unsuported stud. Gun ho attitudes have no truck with sound, safe engineering.

Post by **bmcecosse** » Thu Dec 08, 2005 10:28 am

Ah - taper nuts! Far far better to use sleeve nuts which fit inside the wheel stud bore and clamp the wheel tightly against the drum face. The wheel is then correctly located and very firmly clamped. I would not consider using taper nuts for anything more than standard steel wheels.

Post by **Onne** » Thu Dec 08, 2005 5:00 pm

Please do if you feel save that way BMC, but I think Jonathon might know what he is talking about, since he speciales in upgrading Minors.
And he does it well!

Post by **bmcecosse** » Thu Dec 08, 2005 7:57 pm

Maybe so - but I don't fancy alloy wheels with 4mm clearance on the studs held on with taper nuts !!!! All the alloy installations I have used have the proper sleeve nuts that both centre and grip the wheel. Used to make them by boring the centre of largish Allen cap bolts (threads cut off !) - and turning them to be a snug fit in the wheel stud holes.