15" or 17" wheels and tires
09-12-2003, 11:35 AM
#21
CFOT Attention Whore
Re: 15" or 17" wheels and tires (mrvette)
hey, GENE. i agree with you on the geometry issue and am also looking for a solution to that particular design limitation. however, if you drive fairly agressively, you could dial in a bit more negative camber in the front and the toe wear will even out. i know it sounds odd, but then again, i'm the type that speeds up for corners!
:jester
granted, my car doesn't see constant street duty but for a few years i was averaging about 4000 miles a year. with -1.5* front camber, i still got an even wear pattern.
another tip to this is severly restrict the amount of body roll in the car and that will limit the camber change also.
:jester
granted, my car doesn't see constant street duty but for a few years i was averaging about 4000 miles a year. with -1.5* front camber, i still got an even wear pattern.
another tip to this is severly restrict the amount of body roll in the car and that will limit the camber change also.
09-12-2003, 12:18 PM
#22
Race Director
Re: 15" or 17" wheels and tires (munday)
maybe i should just keep the 17's on for daily driving and road racing and put the 15's on for drag racing at the track........
Just my $.02 worth (and this is REALLY gonna pee-off a lot of C3-owners here.....), but I think C3s with the big, gaudy over-sized wheels (17" and up), kinda look 'ricey' (send all hate mail to..... ), or look like 'Hot Wheels' and 'Johnny Lightnings' toy-cars (wheels & tires out-of-scale with the body).
The only exception I like are the 17" chromed ZR1 wheels & tires; it still says 'Corvette', instead of 'whooga-whooga-isk'/'Fast & Frivolous'/gangsta-rap/pimp-daddy.....Some of them look like Elton John, showing-up for a concert circa 1973.......
OK, my complaint department is now open..... :D
09-12-2003, 02:24 PM
#23
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Re: 15" or 17" wheels and tires (Glensgages)
Just my $.02 worth (and this is REALLY gonna pee-off a lot of C3-owners here.....), but I think C3s with the big, gaudy over-sized wheels (17" and up), kinda look 'ricey' (send all hate mail to..... ), or look like 'Hot Wheels' and 'Johnny Lightnings' toy-cars (wheels & tires out-of-scale with the body).
The only exception I like are the 17" chromed ZR1 wheels & tires; it still says 'Corvette', instead of 'whooga-whooga-isk'/'Fast & Frivolous'/gangsta-rap/pimp-daddy.....Some of them look like Elton John, showing-up for a concert circa 1973.......
OK, my complaint department is now open..... :D
:lolg: :lolg: :lolg:
Just Kidding!! Everyone is entitled to an opinion.
Might be the wrong one but....
:D
09-12-2003, 02:45 PM
#24
Racer
Re: 15" or 17" wheels and tires (Glensgages)
Just my $.02 worth (and this is REALLY gonna pee-off a lot of C3-owners here.....), but I think C3s with the big, gaudy over-sized wheels (17" and up), kinda look 'ricey' (send all hate mail to..... ), or look like 'Hot Wheels' and 'Johnny Lightnings' toy-cars (wheels & tires out-of-scale with the body).
09-12-2003, 04:52 PM
#26
Team Owner
Re: 15" or 17" wheels and tires (Glensgages)
Glen, I totally agree anything larger than 17" is ricey looking, but you gotta admit those stock for a '92 vette rims looks ok on a shark with 50 series tires...one step up from the 40 series the C4 came with....it fills the shark's wells nicely to nearly original diameter, rides smoother for the extra height, and still gives the wider rubber....and I don't think for a VETTE, it's one bit ricey....
Which was another consideration on using a stock C4 style rim....as it's still VETTE all the way, as opposed to those UGLY CHROMED POS some people like....not that is RICE....no mistake about it....
flame suit on.....
GENE :D :eek: :cool: :reddevil :lolg: :smash: :smash: :cheers: :party:
Which was another consideration on using a stock C4 style rim....as it's still VETTE all the way, as opposed to those UGLY CHROMED POS some people like....not that is RICE....no mistake about it....
flame suit on.....
GENE :D :eek: :cool: :reddevil :lolg: :smash: :smash: :cheers: :party:
09-12-2003, 06:20 PM
#27
Melting Slicks
Re: 15" or 17" wheels and tires (Les)
Les,
Thanks for making my day. :thumbs: I'm pretty confident that if I had C-4 wheels on my car, I wouldn't get too many comments like yours. :lol:
Thanks for making my day. :thumbs: I'm pretty confident that if I had C-4 wheels on my car, I wouldn't get too many comments like yours. :lol:
09-12-2003, 06:59 PM
#28
Re: 15" or 17" wheels and tires (foundvettelifeisgood)
I get compliments on mine all the time. I really liked the idea of keeping my car all "corvette". That said, I really like your car too :cheers:
09-12-2003, 07:12 PM
#29
Melting Slicks
Re: 15" or 17" wheels and tires (Zack Wenning)
Zach,
Having seen yours, I take that back. Your car looks way :cool:
I'm just a sucker for offset. The deeper the better. :cheers:
Having seen yours, I take that back. Your car looks way :cool:
I'm just a sucker for offset. The deeper the better. :cheers:
09-12-2003, 08:06 PM
#30
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Re: 15" or 17" wheels and tires (munday)
As long as the diameter of the wheels and tires don't change there shouldn't be a problem, actually you'll see improved handling because of the lower profile. :thumbs:
09-12-2003, 11:05 PM
#31
Le Mans Master
Re: 15" or 17" wheels and tires (Crickett)
Mike your friend was more correct than most are willing to give him credit for.
GM spent a great deal of effort engineering a suspension that could take advantage of the tire technology that existed at the time. They did this using a 15X8 inch wheel with a specific offset. If you install an 8 inch wheel with a different offset you will compromise the suspension geometry. The same would apply if you use a wider wheel that adds the width to the outside or the inside. It's a matter of balance. You could compensate for this by using a wider (or narrower for that matter) wheel that adds width equally to the inside and outside. If this sounds complicated, it really is. And the more you alter the width without compensating, the more it will compromise the suspension geometry.
What does this have to do with diameter of the wheel, well again it's a matter of balance. Increasing the diameter of the wheel with a lower profile tire may maintain the same overall diameter, but it will compromise the stock shocks and sway bars the car came with. This compromise may make the car handle better, but will affect the ride. Again you can compensate, this time by changing your shocks and/or sway bars to recapture ride quality.
The point of all this is that changing wheels and tires is not as simple as you might think. Your suspension is a total package that includes tires, wheels, shocks, springs and even alignment. GM engineered a balanced package that provided excellent handling and ride quality. Don't delude yourself into thinking that you can simply switch to a 17 inch wheel and not affect this balance. The more you alter the balance, the more you will compromise the handling and/or ride of the car.
Do some research or consult a suspension specialist and you will be delighted with the results. To do otherwise can really be a crap shoot.
GUSTO
GM spent a great deal of effort engineering a suspension that could take advantage of the tire technology that existed at the time. They did this using a 15X8 inch wheel with a specific offset. If you install an 8 inch wheel with a different offset you will compromise the suspension geometry. The same would apply if you use a wider wheel that adds the width to the outside or the inside. It's a matter of balance. You could compensate for this by using a wider (or narrower for that matter) wheel that adds width equally to the inside and outside. If this sounds complicated, it really is. And the more you alter the width without compensating, the more it will compromise the suspension geometry.
What does this have to do with diameter of the wheel, well again it's a matter of balance. Increasing the diameter of the wheel with a lower profile tire may maintain the same overall diameter, but it will compromise the stock shocks and sway bars the car came with. This compromise may make the car handle better, but will affect the ride. Again you can compensate, this time by changing your shocks and/or sway bars to recapture ride quality.
The point of all this is that changing wheels and tires is not as simple as you might think. Your suspension is a total package that includes tires, wheels, shocks, springs and even alignment. GM engineered a balanced package that provided excellent handling and ride quality. Don't delude yourself into thinking that you can simply switch to a 17 inch wheel and not affect this balance. The more you alter the balance, the more you will compromise the handling and/or ride of the car.
Do some research or consult a suspension specialist and you will be delighted with the results. To do otherwise can really be a crap shoot.
GUSTO
09-13-2003, 04:04 AM
#32
CFOT Attention Whore
Re: 15" or 17" wheels and tires (GUSTO14)
hmmm,
gusto, sorry to say i must disagree somewhat.
first off, if the rim diameter stays the same and the offset stays the same, you haven't changed anything and that relationship to bearing life will be completely unnoticable.
second, g.m. did a great deal of engineering to design a suspension to try and save people from over-driving their abilities. hence, the discussion GENE, norval, PROSOUTH, myself and many others have had attempting to solve the engineered-in understeer inherent in cars of that era and even to this day. an upgrade in tires/wheels can reduce this simply because of less sidewall deflection.
you are correct in that it will throw the 'balance' off. that balance being the unsprung weight. i think we discussed this somewhere else in this thread but a set of custom made 17" wheels with identical offset and width will, assuming their aluminum, significantly reduce the amount of unsprung weight. this has effects in the linear planes as well as centrifugal ramifications. in the 'linear' plane, it will now take less spring rate to control a lighter tire over undulations. also making it easier for the springs and shocks to keep the non-linear movements in check and reduce the forces induced in the frame.
the centrifugal forces will be less for the same reason that people switch to light weight flywheels. wheels have to obey the same laws of physics. an object at rest tends to stay at rest, an object in motion tends to stay in motion. we've all heard that. wheels and tires are no different.
personally, i believe most of these variables will be very difficult for the average person to even notice. more often, there will be a perceived difference more than a measurable one.
the one thing i can absolutely assure you of (from personal experience), were you to take a factory aluminum 15x8 and compare the weight to, say, the 17x8.5 sawblade, there would be a small but discernable difference. now you take a 255/60-15 and weigh it against a 255/40-17 and there will be a significant difference. somewhere in the neighborhood of 25% less, and that's centrifugal weight, the worst kind.
i'm not trying to be disagreable. this may be a little complicated, but it's certainly not rocket science.
gusto, sorry to say i must disagree somewhat.
first off, if the rim diameter stays the same and the offset stays the same, you haven't changed anything and that relationship to bearing life will be completely unnoticable.
second, g.m. did a great deal of engineering to design a suspension to try and save people from over-driving their abilities. hence, the discussion GENE, norval, PROSOUTH, myself and many others have had attempting to solve the engineered-in understeer inherent in cars of that era and even to this day. an upgrade in tires/wheels can reduce this simply because of less sidewall deflection.
you are correct in that it will throw the 'balance' off. that balance being the unsprung weight. i think we discussed this somewhere else in this thread but a set of custom made 17" wheels with identical offset and width will, assuming their aluminum, significantly reduce the amount of unsprung weight. this has effects in the linear planes as well as centrifugal ramifications. in the 'linear' plane, it will now take less spring rate to control a lighter tire over undulations. also making it easier for the springs and shocks to keep the non-linear movements in check and reduce the forces induced in the frame.
the centrifugal forces will be less for the same reason that people switch to light weight flywheels. wheels have to obey the same laws of physics. an object at rest tends to stay at rest, an object in motion tends to stay in motion. we've all heard that. wheels and tires are no different.
personally, i believe most of these variables will be very difficult for the average person to even notice. more often, there will be a perceived difference more than a measurable one.
the one thing i can absolutely assure you of (from personal experience), were you to take a factory aluminum 15x8 and compare the weight to, say, the 17x8.5 sawblade, there would be a small but discernable difference. now you take a 255/60-15 and weigh it against a 255/40-17 and there will be a significant difference. somewhere in the neighborhood of 25% less, and that's centrifugal weight, the worst kind.
i'm not trying to be disagreable. this may be a little complicated, but it's certainly not rocket science.
09-01-2004, 10:20 PM
#33
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Originally Posted by LakotasRose
Well gonna throw in my 2 cents.
I went to 17s..and there is a BIG difference in the handling!! I also lowered my Vette on the front by 2 inches...and THAT made an even BIGGER difference.
NO way I would go back to 15s.
I went to 17s..and there is a BIG difference in the handling!! I also lowered my Vette on the front by 2 inches...and THAT made an even BIGGER difference.
NO way I would go back to 15s.
John
09-01-2004, 10:43 PM
#34
Melting Slicks
Just because we like vintage cars, doesn't me we like vintage threads! 
Actually this is pretty well timed as I'm looking into wheels at the moment... and a good discussion too.
-Chris
Actually this is pretty well timed as I'm looking into wheels at the moment... and a good discussion too.
-Chris
09-02-2004, 04:30 AM
#35
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MY TOP TEN THOUGHTS
1. Y-Yeah thats why nascar runs 15 inchers
2. GM ALLLLMOST used 17's in 1969
3. HEY did'nt the Genaral Lee have 15's? That car flew!
4. One and only good reason to run 15's RALLY WHEELS
5. GM almost used 15's on the C6....
6. Does your friend drive a FORD?
7. The differance beetween 15 and 17 is 2 inches (its a big deal to my girlfriend)
8. 17 is almost 18 ... ooops were talkiing wheels not girls
9. Maybe your friend does'nt want you to have too much BLING
10. One jack 20 lugnuts and you can change them back if you want
1. Y-Yeah thats why nascar runs 15 inchers
2. GM ALLLLMOST used 17's in 1969
3. HEY did'nt the Genaral Lee have 15's? That car flew!
4. One and only good reason to run 15's RALLY WHEELS
5. GM almost used 15's on the C6....
6. Does your friend drive a FORD?
7. The differance beetween 15 and 17 is 2 inches (its a big deal to my girlfriend)
8. 17 is almost 18 ... ooops were talkiing wheels not girls
9. Maybe your friend does'nt want you to have too much BLING
10. One jack 20 lugnuts and you can change them back if you want
09-02-2004, 06:44 AM
#36
that guy is saying that wheel size has an impact on geometry, that's not true. It only impacts the scrub radius due to wheel offset & tire centerline. If the total diamter is larger the axix centerline for the kingpin will move outboard in the plane of road surface. That's the ONLY thing that changes, the rest of the geometry is set bu the cross shaft positions, kingpin height & angle (and the wheel; alignment settings)
So there 17" wheels have no impact on geometry at all.
The fact that the geometry does not particulary suit 17"wheels with low profile tires is somewhat true, if you set the gactory settings. Then camber is not correct (not that it is any good for the modern 15" tires anyway) but you could get a situation where the tire contact patch is deminished because of a camber angle and the tire wall not having the flex that the 15" one has to form a good footprint. Shocsk don't have an influence here as do sway bars since thiss camber curve is a result of the suspension design. You can install stuffer sway abrs and decrease body roll and then dial in enoygh static camber to counteract the camber curve resulting from the stock geometry but other than that there is no influence.
GM may have done a lot of research but the real problem is in the rear, not so much in the front. Granted, the front could have been better, the lower control arms are terribly long and the angle between lower and upper is not particulary great but that's nothing compared to the toe problem in the rear suspension, which is a result of trying to do things the cheap way. A trailing arm rear suspension like we have will introduce a terrible toe control problem that gets worse the further the suspension is allowed to travel. This causes a rear oversteer and this is the reason why the car gets so hairy to handle when you really get on it.
1. Y-Yeah thats why nascar runs 15 inchers
Rules, Champcars, F1, they all have 15" rims. In F1 you will actually see a tire witha very soft sidewall so it maintains adhesion to the tarmax under heavy cornering. You will sometimes even see the tire wiggle on it's axis, look at Micheal Schumachers Ferrari in close up (cockpit) shots and look at the tire, you will see it doing this. The teams would all instantly swap to 17" if they were allowed, look at the gigantic wheels they use in DTM, GTS and those kinds of racing classes, the larger wheels have far more benefits than the tire alone, thing larger rotors.
2. GM ALLLLMOST used 17's in 1969
I think it was 16", I have pics of a 16" aluminium wheel on a prototype 1983 vette and they are the same as the late alu C3 wheels, only larger. Could be that they were 17" but they look like 16s.
So there 17" wheels have no impact on geometry at all.
The fact that the geometry does not particulary suit 17"wheels with low profile tires is somewhat true, if you set the gactory settings. Then camber is not correct (not that it is any good for the modern 15" tires anyway) but you could get a situation where the tire contact patch is deminished because of a camber angle and the tire wall not having the flex that the 15" one has to form a good footprint. Shocsk don't have an influence here as do sway bars since thiss camber curve is a result of the suspension design. You can install stuffer sway abrs and decrease body roll and then dial in enoygh static camber to counteract the camber curve resulting from the stock geometry but other than that there is no influence.
GM may have done a lot of research but the real problem is in the rear, not so much in the front. Granted, the front could have been better, the lower control arms are terribly long and the angle between lower and upper is not particulary great but that's nothing compared to the toe problem in the rear suspension, which is a result of trying to do things the cheap way. A trailing arm rear suspension like we have will introduce a terrible toe control problem that gets worse the further the suspension is allowed to travel. This causes a rear oversteer and this is the reason why the car gets so hairy to handle when you really get on it.
1. Y-Yeah thats why nascar runs 15 inchers
Rules, Champcars, F1, they all have 15" rims. In F1 you will actually see a tire witha very soft sidewall so it maintains adhesion to the tarmax under heavy cornering. You will sometimes even see the tire wiggle on it's axis, look at Micheal Schumachers Ferrari in close up (cockpit) shots and look at the tire, you will see it doing this. The teams would all instantly swap to 17" if they were allowed, look at the gigantic wheels they use in DTM, GTS and those kinds of racing classes, the larger wheels have far more benefits than the tire alone, thing larger rotors.
2. GM ALLLLMOST used 17's in 1969
I think it was 16", I have pics of a 16" aluminium wheel on a prototype 1983 vette and they are the same as the late alu C3 wheels, only larger. Could be that they were 17" but they look like 16s.
09-02-2004, 10:54 AM
#40
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I just got 255/45-17 on my 79 on the advice of other forum members, mounted on 8" Boyds Smoothie II's Love the look and ride, get sooooo many compliments its embarrassing. The front fits very well but the back is real close to the E brake cable, if you were to go wider in the back you would need spacers or a different offset wheel for the rear.
