 |
924Board.org
Discussion Forum of 924.org
|
| View previous topic :: View next topic |
| Author |
Message |
924RACR
Joined: 29 Jul 2001
Posts: 9064
Location: Royal Oak, MI, USA
|
 Posted: Wed Jul 27, 2005 11:05 pm Post subject: Tire Review on my 931 - Sumitomo HTR+ vs. BFG G-Force KDWS |
 |
|
I just switched from the BFG's (worn out and one separated cord) to the Sumitomos and HAD to post back my observations already. It's been a HUGE impact in performance. Size is stock 205-55-16, and these are both ultra-high performance all-season tires, with some snow capability. But the Sumitomos have a much softer sidewall than the BFG's.
1: Tramlining - gone after switching to the HTR+'s. Directional stability is also much better
2: Ride Quality - vastly improved
3: Steering weight - much reduced with the Sumitomos.
4: Road noise - noticeably reduced, although I've noticed pretty much every tire tends to get a bit noisy towards the end of its life (BFG's were at wear bars in front, close to it in rear).
It is really amazing what a difference the sidewall stiffness and just the change of tire can make in the car. I've previously found the car very stiff and harsh to drive, especially with the Detroit roads, in spite of rebuilding the suspension and putting in new Bilsteins. Now it's much nicer, lighter, more responsive. It responds to the steering inputs much better, more quickly. Also low-speed steering effort is much better, with the manual steering.
Obviously this car is set up to want a decent bit of compliance in the tire sidewall to drive properly; both ride compliance and steering response.
The BFG's are great in a high-performance setting, but they're so stiff for this car I'd say they're basically undesireable unless you are using them for the track - in which case you could probably do better (more pure-track-oriented tires are out there).
The Sumitomos were much less than the BFG's too - about $60 at tirerack.com vs. nearly 100 for the BFG's.
The car is a whole lot more fun to drive now; sure, the upper limit of performance may be reduced, but I don't even want to explore that on the street, and the stuff that matters when commuting - comfort and ride and handling response - is much better. I now feel a whole lot more motivated to daily drive this car than I used to! Sure, my minivan with it's Arctic Air AC and leather seats may be a bit more comfortable, especially in the heat wave we're having, but at least now the Turbo is a lot more comfortable - not simply something to be tolerated for the driving experience.
I'd say, in summary, the BFG's made my car feel awfully close to my racecar - real sensitive, twitchy, feel every bump, tough to steer, but can do amazing things in the corners.
Choose accordingly.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
|
| Back to top |
|
 |
augidog
Joined: 03 Mar 2003
Posts: 1360
Location: New Jersey
|
| Posted: Thu Jul 28, 2005 8:37 pm Post subject: |
|
|
Thanks for the real life results. I wish they made an all season. So high speed rating sidewall strength really makes a difference. Good to know.
_________________
1978 924 95 mile daily driver.
Audi TB/POR174M/High Flow Cat/2.25" exhaust
I knew that positive thinking thing wouldn't work. |
|
| Back to top |
|
|
924RACR
Joined: 29 Jul 2001
Posts: 9064
Location: Royal Oak, MI, USA
|
| Posted: Thu Jul 28, 2005 10:11 pm Post subject: Re: Tire Review on my 931 - Sumitomo HTR+ vs. BFG G-Force KD |
|
|
| 924RACR wrote: | | I just switched from the BFG's (worn out and one separated cord) to the Sumitomos and HAD to post back my observations already. It's been a HUGE impact in performance. Size is stock 205-55-16, and these are both ultra-high performance all-season tires, with some snow capability. |
| augidog wrote: | | So high speed rating sidewall strength really makes a difference. Good to know. |
No, not exactly. I'm talking about sidewall stiffness - you can actually feel this by hand on the unmounted tire. You're talking about speed ratings (like S, V, and Z) - these are something completely different. The Sumis are V-rated, the BFG's were Z-rated, but this is not at all closely related to their stiffness and compliance in ride and handling. The BFG's are a VERY handling-oriented tire, with a massive compromise in ride quality. The Sumitomos are, by contrast, much more ride-oriented, sacrificing some handling ability.
It's important at this point to understand how tires and correspondingly vehicle chassis designs have evolved since our cars were designed. When our cars came out, even a 60-series tire was considered low-profile and stiff. Nowadays 35-45 is considered agressive. Remember this is the ratio between the sidewall height and the tread width (still no major relation to stiffness - as I've shown two tires with the same profile number can have vastly different sidewall stiffnesses).
Anyway, back on topic. The tire is a major component of the vehicle's suspension, and the suspension is designed to work with a particular type of tire. Those tires function as an additional spring and damper element at each corner. Our cars were designed to work with what were high-performance tires at the time - which still had tall sidewalls (for these days). More modern tires may effectively function as stiffer springs and dampers. More modern cars are designed to work with these higher spring and damper rates, yet still provide decent ride. Our cars appear to rely quite a bit on the tire to provide a decent ride - not surprising given how light they are (relative to more modern cars).
So do the same comparison, say, on an E36 BMW, you'd come away with a substantially different experience. Putting a tire like these BFG's on our cars gives very similar results to putting a track suspension on; much stiffer, harsher ride, but much crisper response and a much more taut-feeling vehicle.
This did not suit my personal needs for the vehicle, since it's my daily driver and needs to be able to handle Detroit roads, some of the worst in the country. I likewise have the 14mm rear swaybar which is not ever going to go on this car, since it would make ride worse in return for a handling benefit I never plan to use. I have other cars to race or drive hard on track. To each his own, that's why I said choose accordingly.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
|
| Back to top |
|
|
Smoothie
Joined: 01 Jan 2003
Posts: 8032
Location: DE (the one near MD, PA, NJ)
|
| Posted: Fri Jul 29, 2005 6:29 am Post subject: Re: Tire Review on my 931 - Sumitomo HTR+ vs. BFG G-Force KD |
|
|
| 924RACR wrote: | | Tramlining - gone after switching to the HTR+'s. Directional stability is also much better |
This is interesting (actually it's all interesting  , but that line especially), because I recently finished wearing-out a set BFG KDWS and replaced them with Kumho Ecsta ASX in the same size - 205/55R16. -And I've noticed less of some weirdness in the handling that might be described as tramlining and which I had been attributing to the different offset of the wheels - 911 Fuchs that leave the tires sitting approx 17mm further out than the stock flat wheels. The weird handling was most noticable along a certain length of road where there's a slight valley running in the direction of travel - a seam between applications of asphalt that happened to lie in the path of the right-side tires when driving down the middle of the lane. It would feel like the tire was catching on the seam then being pulled to one side, then the other - a kind of squirrely motion. I've driven the same piece of road in at least two other vehicles and didn't have the same experience with them. Whether it's called tramlining, squirreling or whatever it is, it's been lessened with the change from BFG KDWS.
_________________
"..it's made in Germany. You know the Germans always make good stuff."
'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox |
|
| Back to top |
|
|
924RACR
Joined: 29 Jul 2001
Posts: 9064
Location: Royal Oak, MI, USA
|
| Posted: Fri Jul 29, 2005 9:09 am Post subject: |
|
|
I experienced exactly that feeling with the stock size KDWS's on the stock rims.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
924 FAQ (Technical)
