[kylemad]

Hi guys, I'd appreciate some help on this topic.

For the past few weeks, my 2008 Sport GTS has been suffering from a bouncy ride, at both low and high speeds, and I can't isolate the cause. The car is unsettled on even the smoothest of roads and at speeds from 40km/h and beyond. When I say bouncy, I don't mean that the ride is too hard or soft. The car just seems to shake about slightly for no reason, almost as if there are invisible but distinct imperfections on the ground. The steering is fine though.

A few months ago, I swapped my tyres from P-zeroes to Pilot Sport 2s and in doing so, had to settle with a changed profile for the rear tyres from 295/30 to 295/35 cuz the PS2s aren't available as 20-inch 295/30s.

My question is: could the changed profile of the tyres could be the cause of this bouncy ride? If so, why would this problem only turn up over a month after the tyres were changed? Everything worked perfectly for a month and in fact, I was very pleased with the ride from the new tyres.

One of the salesmen at the dealership said that it might be so because the onboard computers function based on stock tyre profiles. However, I pointed out that the Sport GTS uses fixed dampers and not the skyhook adaptive suspension, so I don't see why the ride would be affected by the computer's accounting. In any case, a visual inspection of the suspension parts at the dealer didn't turn anything up.

I'll try to find a spare set of 295/30s and run the car on them to see whether or not there's a difference. But in the meantime, does anyone have any ideas?

 

[JGT]

I had a very bouncy ride when I got mine back from the dealer once.....they had put 4 Bar (!!!!) in all tires (guidance is 2,2bar). After putting the right pressure things were normal again. I did not have the tire pressure monitor and maybe you do so maybe not your case. The dealer was very apologitic after I told them....

 

[JGT]

By the way I am putting the 20' wheels of my GRancabrio on the QP (simulation attached) but the dealers advosed strongly against using the same tires (QP are 285/30 and GC 285/35) SO I will use the tires on the new Neptune wheels for the cabrio and buy the "correct" tires for the QP.

A question for you with 20' on the QP: my dealer said the ride would be more sportive, nicer look etc but to be extremely carefull with potholes. Since their is so little ruber to pñrotect the wheel they get damaged very easy they warned me. They get warped 20' wheels all the time.....is this true? (that is also why i wanted to go for the 35 to have a bit more rubber and air)

 

[kylemad]

I had a very bouncy ride when I got mine back from the dealer once.....they had put 4 Bar (!!!!) in all tires (guidance is 2,2bar). After putting the right pressure things were normal again. I did not have the tire pressure monitor and maybe you do so maybe not your case. The dealer was very apologitic after I told them....

I have the TPMS and it reads 2.3 on each tyre. Just pumped the tyres recently and the issue remains!

 

[06MCVICTORY]

My only thought would be that they did not balance the tires properly

 

[mowlas]

Balancing seems the most obvious culprit. Sometimes the balancing counterweights can come off if the wheel was not cleaned before applying. I would also double the manual for exact tyre pressures. On my sport gt it is meant to be 2.0 on the rears and 2.2 on the fronts. Not sure about the GTS?

 

[elambo]

Sometimes the balancing counterweights can come off if the wheel was not cleaned before applying.

That was my thought, too.

 

[RaCinStylez]

Could also be the composition of the tires. Some tire side walls are made softer than others. Perhaps it may be a combination of wrong tire size, differant composition, and wrong tire pressure.

 

[kylemad]

if i'm not wrong, unbalanced tyres would result in some steering feedback, but there isn't any difference in the steering at the moment. i've yet to send the car in, but will do so soon.

 

[mowlas]

The Sport GTS had unique stock wheel dimensions (I believe they were wider than the earlier Sport GT's) and I am pretty sure its suspension is finely tuned to work with a specific dimension of tyre. Not sure about all the dimensions on the pilot but the different aspect ratio could implies that you have extra inner height on the sidewall. This could be causing undue pressure on the sidewalls given the wheel rim is expecting an aspect ratio of 30 not 35. I suspect this makes the tyre more bouncy. The interaction between the finely tuned suspension and the different tyre could be causing the bounciness you are experiencing.

Wonder if Jeff from FD can comment here?

Regardless of the problem, it may be progressive as you didn't notice it at first and I would therefore take no unnecessary risks until it gets sorted. Sounds like the dealer had no clue. Have you tried contacting Maserati MNA?

Good luck, hope it gets sorted soon.

 

[mowlas]

Could also be the composition of the tires. Some tire side walls are made softer than others. Perhaps it may be a combination of wrong tire size, differant composition, and wrong tire pressure.

As RaCinStylez mentioned, the 2008 QP GTS was developed to work with very specific tyres. Saw the following quote in the article in the link below:

"The braking system on the Quattroporte Sport GT S employs new single-piece, six-piston calipers in the front and has tyres developed especially for this car (front 245/35-R20 and rear 295/30-R20). These larger tyres provide improved traction while the new tyre compound works with the brakes and suspension set-up to assure even better handling and a more involving drive."​

http://www.seriouswheels.com/cars/2008/top-2008-Maserati-Quattroporte-Sport-GT-S.htm

Cheers

 

[maseratisportgts]

Its not the tires.... you are a new QP Sport GTS owner? I have a 2008 Sport GTS Quattroporte, one of the first ones in the country. Where are you from? What roads do you ride? Its springs, yes which means its "Old School Racing Springs" just like I like them. If you are looking for a smooth ride, get a benz, I have 2 of them for family driving. I have to be honest- the sport GTS has old school springs like bilsteins shocks, and I must say, they cut up any and all corners/roads I have been on handling wise, because the handling is so tuned. I ride on 20" HRE 540R chrome rims, I think the tire size is the same as OEM for a 20" rim as we have, and I put on Vredestein Sessanta tires on, and they are amazing for the price. What you have there is culture shock- What car did you drive before? The QP is not suited to have air shocks like a Mercedes Benz- It is a sports car in a sedan body if I can describe it that way. Learn to live, and love what you have. You are a lucky man to have what I have, for I hath worked my ass off to acquire perfection in a 4 door realization. If you still don't get it, get this- cars are never perfect, only you can accept/realize perfection in your mind. To me, my 2008 Sport GTS is perfect in every way, except for the fact that I have to still pay the bills on it!

 

[kylemad]

As RaCinStylez mentioned, the 2008 QP GTS was developed to work with very specific tyres. Saw the following quote in the article in the link below:

"The braking system on the Quattroporte Sport GT S employs new single-piece, six-piston calipers in the front and has tyres developed especially for this car (front 245/35-R20 and rear 295/30-R20). These larger tyres provide improved traction while the new tyre compound works with the brakes and suspension set-up to assure even better handling and a more involving drive."​

http://www.seriouswheels.com/cars/2008/top-2008-Maserati-Quattroporte-Sport-GT-S.htm

Cheers

thanks for the input! i read the press releases too and figured that all the talk of 'specially developed tyres' was nothing more than marketing rubbish. now i'm thinking it might not be so.

the puzzling thing is that the tyres worked perfect for a few weeks before this bouncy issue came about. and Maseratisportgts, i've had the car for two years, so i know how firm it's supposed to feel. trust me, the car isn't behaving like it's supposed to. anyway, like i said, 'bouncy' here doesn't mean 'bumpy' or 'hard, crashing ride'. it just seems to boing about for no good reason.

 

[mowlas]

i read the press releases too and figured that all the talk of 'specially developed tyres' was nothing more than marketing rubbish. now i'm thinking it might not be so.

the puzzling thing is that the tyres worked perfect for a few weeks before this bouncy issue came about.

My thought was less that the tyres were specially developed for the GTS but more that the GTS's suspension was finely tuned to work with a very specific tyre with specific ride charecteristics. A final thought is that if the rear tyres are more bouncy than the fronts (for the possible reasons I stated earlier) then you might also get a see-sawing effect between the front and rear tyres as well as interplay with the suspension system.

We need Columbo to help us hypothesise why the problem only appeared after a few weeks! Do the sidewalls look OK? Could it be a progessive issue?

Dying to know what the real issue is now...

 

[mowlas]

A question for you with 20' on the QP: my dealer said the ride would be more sportive, nicer look etc but to be extremely carefull with potholes. Since their is so little ruber to pñrotect the wheel they get damaged very easy they warned me. They get warped 20' wheels all the time.....is this true? (that is also why i wanted to go for the 35 to have a bit more rubber and air)

JGT,

Have been running for 9 months and 6K miles on stock 20" wheels on my QP Sport GT now. The roads in London are not great at the moment and we quite a lot of damage from a freezing cold snap this winter. Have had no problems at all. I did hit a very deep pothole about 6 months ago but that just scuffed the rim which I had repaired. It may be that your dealer is worried that the Grancabrio wheels are not designed to handle the weight of a QP?

-- Ignore the last remark edited as I understand the QP and Grancabrio almost weighh the same!

 

[JGT]

Thks!


I asked for the Sport GT wheels initially (also 20') when the dealer "warned" me for warped wheels. But finally I have put my GC wheels on my QP and I really love them. Will post pictures in a new thread.

 

[alvav]

It is most definitely the profile of the tires!! The real negative is that the front tires remained stock. So the computers "expect" a certain percentage of revolutions of the front axles with respect to the revolutions of the rear. And without the increased profile, the computer is not receiving what it expects. This can create many problems and issues, including permanent damage to the drivetrain.

 

[maseratisportgts]

The QP Sport GTS suspension was tuned to work with the Stock Wheels that come with it for optimal grip and performance. The P Zero that come with the car in stock form are the best tires grip wise in dry conditions from my experience. The car is very nimble and agile and feels very lightweight for its size when on the stock wheel set up. It is the best set up for the QP, it was tuned to run that way. As for aftermarket wheels, I'm running HRE 20" rims with Vredesteins. I also had to run 10mm spacers so the wheels could clear the larger brake calipers for my rears. The car looks great and the ride is still smooth but reacts/feels totally different than in stock trim. Totally. It feels heavier and at top speeds I feel acceleration suffers slightly from running chrome rims. In the Wet the vredestein offers much better grip than the P zeros for a lot less money. I like both, they are different set ups. As I got a deal on my HRE"s and it cost about the price of only 1 stock rim, in new york, I rather run the aftermarket in case I hit a pothole or something worse, I'm not totally screwed. Your tires I think are the most imortant decision for what you want ride wise, because they are the only contact patch you have on the actual road. By the way, I had michelin PS2's on them first because they came that way, and it was hands down the best tire all around except for cold weather, then it would get skittish. You can't win. You need different tires for different conditions in your area and season.

 

[mowlas]

thanks for the input! i read the press releases too and figured that all the talk of 'specially developed tyres' was nothing more than marketing rubbish. now i'm thinking it might not be so.

the puzzling thing is that the tyres worked perfect for a few weeks before this bouncy issue came about. and Maseratisportgts, i've had the car for two years, so i know how firm it's supposed to feel. trust me, the car isn't behaving like it's supposed to. anyway, like i said, 'bouncy' here doesn't mean 'bumpy' or 'hard, crashing ride'. it just seems to boing about for no good reason.

Hi Kylemad,

Out of interest, did you get to the bottom of the problem? Hope it is resolved now...

Shak

 

[kylemad]

hey, thanks for asking. the car was brought to the workshop for extensive analysis. the suspension and everything was thoroughly checked, but nothing was found. in the end, we ran the car on a new set of tyres with the right profile (295/30 instead of 295/35) and the ride was much smoother, with most of the bounce eliminated. thus, it was decided that the tyres were at fault! still doesn't explain why the bounciness only manifested itself a few weeks after i got the 295/35s though.

despite the problems, will be sticking with the 295/35s since they aren't cheap. will be sure to change back to the stock size once this set wears out!