TR4/4A Chassis Buffeting(?)

[RJS]

Hi

Driving any where b/t 55 and 65 mph I seem to be getting a "buffeting" feeling under the car. It feels like a lot of air getting under the chassis and vibrating the entire car. Any ideas? It's always been there (owned 23 years) and seems to disappear over 65mph. It's a disconcerting feeling which makes driving on the parkway a bit "nervy".

Stock/original springs - which I understand intentionally puts the font end ~1/2" higher than the rears. New shocks, ball joints, steering rack and tie rod ends 3 years ago...same feeling. Older wire wheels which, as best I can tell are well balanced.

The buffeting feeling is in the seat of my pants - no shakes in the steering wheel.

I plan on checking the wire wheels for true-ness and run-out. Any other ideas?

Bob

 

[malbaby]

That's a strange one....Is your chassis IRS.

 

[RJS]

Indeed, it is

Bob

 

[mctriumph]

Wire wheels can be bent, but it is a myth that the spokes can "true up" a bent wheel. If you do not have
stainless steel spokes you will not be able to tighten them at all. So if they wobble, they are trash. Only buy
the good stuff(Dayton's) the stainless spokes are wonderful in the long run.
Mad dog

 

[charlie74]

Maybe a problem with a tire…?

 

[NutmegCT]

Just a thought - I had a similar problem (seat vibration) between 50 and 60 mph on my TR3. No vibration through steering wheel.

Turned out to be a failing (worn) u-joint on the driveshaft.

From Hales Automotive . com -

"A bad u-joint can also cause vibration at certain speeds, emanating from the center or rear of the vehicle. If a u-joint is excessively worn, there’s an easy test you can perform. With your foot on the brake, shift the car into reverse. Then, shift into drive. If the vehicle makes a clunking sound, or you can feel it knock one time after engagement, a u-joint is likely the culprit. As it wears out, it doesn’t make a tight connection to the differential and driveshaft, allowing for too much play at the joint."

Try the above and let us know what you find.

Tom M.

 

[Hamish Racing]

Sounds like an alignment and or tyre issues, lack of toe in can make the car feel light and skittish at speed

 

[RJS]

Hi, and thanks Gents,

1) Tom, I tried your test several times and actually pleased/relieved no clunking. I've been really good with relatively new (5 years ago maybe?) u-joints, axle shafts and rebuilt diff (Quantum Mechanics). I also hit all of them each year with the grease gun. BUT, I am now considering if my driveshaft needs balancing or even if the flanges are bent. The reason I say this is b/c in 2003 I had very suspect "British Car Mechanic" replace the u-joints on the drive shaft. Apparently he used the wrong size (?) and a few year later the front driveshaft u-joint failed at speed and I dropped the dive shaft (scary stuff, I was driving 60mph on the parkway when it started to fail and was able to nurse the car to a secondary road before it dropped completely!!). So, definitely something to look into. I'll see if I can locate a drive-line shop nearby and see if they can inspect/balance/rebuild it.

2) Hamish, unlikely alignment. I set alignment in 2021 to 1/16" toe in. Possibly tires. They are Vred Sprint Classics coming up on 9.5 yrs old. Will try rotating wheels though.

At this point, I am leaning towards misshapen wire wheels or driveshaft issues. Will measure wheels next for roundness and run-out.

Thanks again

Bob
PS: Tom, looks like you are in Connecticut, as am I. I see today was the 43rd CTR British Motor Gathering in Wickham Park. If the weather was anything like where I am in SW CT, we had rolling thunder and torrential rain from 10:30am onward

 

[RJS]

Update: measured wire wheels. All within spec of <2.4mm roundness or run-out. Worst wheel was 1.0mm and 1.5mm respectively. Strongly suspecting driveshaft now. Will have to wait...

Bob

 

[NutmegCT]

Bob - rainy here all day in eastern Connecticut.

I'd bet you're on the right track by investigating the driveshaft possibility. "A very suspect British Car Mechanic" - there's a lot of those ...

And a driveshaft failure on the Merritt Pkwy doesn't sound like fun - not to mention any damage it may have caused.

Tom M.

 

[RJS]

Hi

Circling back on this thread, I am now 99.9% the shaking is being caused by the drive shaft being assembled incorrectly and out of phase. See more here: > TR4/4A - Drive Shaft - Prop Shaft Alignment and Balancing <

Bob