Any advice on Optra 'thumping' tire/road noise at 40KPH

[Ravich]

My Optra Royale (1.6 ) has done 15000KM -- regular 185/64 R14 alloy wheels. I find a slighly annoying 'perodic' thumping sound at exacly 40KPH , not below and not above this speed. Apparently from the front tires. Its loud enough to be annoying to some one who is very particular about a cars running condition
Havent checked wheel balance yet but I was puzzled by the exactly at 40 and not above/below symptom. Sound occurs on neutral coasting as well.

Does anyone have any advice /comment to offer ?
Thanks in advance.
Ravich

[akshay1234]

is this everywhere or only on specific types of roads? ive noticed something like this on marine drive in my innova and getz.

[Ravich]

Every road!. I suspect it could be a suspension mech resonance conciding with balance problem at 40kph.
I'll check with the garage and post

[drifter]

It could be a stone in one of your tyre treads. It was at least in my case.

Drifter

[BUSA]

There is a small stone stuck on your front discs, go to GM they will remove it. Faced the same in my 1.8LT a year back. Came at only one particular speed.

[veyron1]

Rotate tyres. Check again. If problem persists, check alignment, balancing & knuckle bushings.

Now this might sound odd, but nevertheless- check if the thumping sound is coming from under the dash, from the driver's side. if yes; check out the speedo gear/cable & rack.

But first, check the front tyres & sidewalls for wear/tear...& check them stones too..

[BaCkSeAtDrIVeR]

Busa, (or anybody else, please) if this only a stone in the tread / discs, why does this happen only at specific speeds? I have seen / heard tyres with patchwork (like when damage to the crossply fabric is repaired with patch) giving out this sound at all speeds; and have noticed transmission / differential components on the verge fo failing complaining at specific speeds / specific gears.
I can understand drifters post.

[BUSA]

Originally Posted by BaCkSeAtDrIVeR

Busa, (or anybody else, please) if this only a stone in the tread / discs, why does this happen only at specific speeds? I have seen / heard tyres with patchwork (like when damage to the crossply fabric is repaired with patch) giving out this sound at all speeds; and have noticed transmission / differential components on the verge fo failing complaining at specific speeds / specific gears.
I can understand drifters post.

Well it happens at specific speed because of resosnance, i can assure you that there is a small stone stuck on the front discs, had the same noise at specific speeds in my Optra too so i know it was a 2 hour job for GM to remove the stone by removing the tyre and the whole disc assembly and then the stone and then putting back the whole assembly.

[BUSA]

Any updates on the problem?

[Ravich]

Originally Posted by BUSA

Any updates on the problem?

Apologies. (My MTNL triband has been out and could not access. )
1. I replaced the suspect wheel with the spare. Noise went down
2. Got all 4 wheels and spare balanced again

Noise went away completely.
Suspect it was balance and resonance.

BTW - do you advise alignment periodically ( 5000 , 10000) even if there is no uneven tread wear or straightline stability is good. ?

[Ravich]

Update on the problem - interchanged suspect wheel with spare, noise reduced. So balanced all wheels. Noise went away completely. Apologies for late update. Broadband problem after shifting house.

Thinking of getting alignment done as well.

[Lukeskywalker]

BTW - do you advise alignment periodically ( 5000 , 10000) even if there is no uneven tread wear or straightline stability is good. ?

It's always good to get the alignment done at periodic intervals (5000kms recommended), that way you don't have to wait till there is uneven wear which is non reversible.

[BUSA]

Getting the alignment right for a Optra aint a easy task since the steering tends to be off and making it straigh is ot of the capability of GM or any other tyre wala.