Wheels

[Tidexcab99]

Alright, for starters I learned so much just from going to Detroit...even though my team didnt compete in any dynamic events....a LONG STORY, just seeing the other universities take the competition "and their engineering students" a lot more seriously than ours did this past year. Anyway being a first year team with no one knowing what to expect we were kind of happy with just passing tech...I guess, well we didnt even start design the thing unitl mid January, so maybe we didnt do so bad for 4.5 months. My question about wheels is 10" or 13" and why(besides cost). Ive done a lot of searching on this site and have gotten mixed results. I know the Douglas 10's must use stiffeners for heavy loading in corners, but do the Kodiak 10's have to have them as well? Just trying to get ideas from the people that know so our car for next car will be ready to go upon arrival...unlike this year. Our team is already starting on our car for next year...long summer and fall for me.

[Tidexcab99]

Alright, for starters I learned so much just from going to Detroit...even though my team didnt compete in any dynamic events....a LONG STORY, just seeing the other universities take the competition "and their engineering students" a lot more seriously than ours did this past year. Anyway being a first year team with no one knowing what to expect we were kind of happy with just passing tech...I guess, well we didnt even start design the thing unitl mid January, so maybe we didnt do so bad for 4.5 months. My question about wheels is 10" or 13" and why(besides cost). Ive done a lot of searching on this site and have gotten mixed results. I know the Douglas 10's must use stiffeners for heavy loading in corners, but do the Kodiak 10's have to have them as well? Just trying to get ideas from the people that know so our car for next car will be ready to go upon arrival...unlike this year. Our team is already starting on our car for next year...long summer and fall for me.

[Beast]

Judges didn't seem to like our 10" wheels and neither did the Hoosier tire guy. Things like cost and weight when it came to tire selection didn't seem to matter.

[Denny Trimble]

Don't forget about the 8" wheel option:
http://students.washington.edu/dennyt/fsae/concordia.jpg

[JonBoy]

Are they funky long swingarms on the rear suspension pivoted from the other side of the car?

[Denny Trimble]

Nope, linear motion rails (see the front upright in this picture). Very unique!

[JonBoy]

Does that mean that theres 2" or so of exposed sliding surface above and below the upright on the rails? what sort of slop did you have?

Next step would be to cut teeth in the rails like a linear actuator and run a fully active suspension.

what are those long bars on the backend of the car then?

cheers
j

[Denny Trimble]

First question - yes. The round rails are fixed, and the uprights slide up and down on them. I think Morgan was the original car company to do this.

Concordia University will have to answer the rest of the questions. I'm just an admirer http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Tidexcab99]

Lets not get too far off topic, however I did see that car and it was very unique. Any more suggestions on wheels?

[fsae_alum]

As Claude Rouelle would say "Show me your tire curves" You need to start looking at tire data (Goodyear). Also mouting the tires becomes a problem as some have pointed out. Cost and availability of tires can also be an issue with 10" rims. Likewise, you may not have the compound selection to choose from either. Weight can be saved with smaller rims and tires CG, and smaller urights, but then brake packaging can become an issue. Also, with smaller spindle height and narrower toe base, it increases the loads on the joints, so any weight savings might be negated by a necessity to increase the robustness of the design to compensate for the load increase. It's all a big trade off. Nobody can tell you what is the correct answer because there isn't one. It's the lesser of 2 evils to some extent and you have to ultimately run the numbers and come to the decision on your own.

[MikeWaggoner at UW]

Looking at the fact that many teams use a single rear brake in the rear, it might be good to use 10's in the rear and 13's in the front, provided you can get adequate rubber.

[Charlie]

Check out the top 5 cars from 2004. They all ran the same tire. Not saying there's not a better one out there, but we've looked pretty hard. Start out by choosing a tire, then choose a wheel to fit it.

What was the top finishing car this year that did not run Hoosiers 13x7?

[MikeWaggoner at UW]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Denny Trimble:
First question - yes. The round rails are fixed, and the uprights slide up and down on them. I think Morgan was the original car company to do this. <HR></BLOCKQUOTE>

I don't know if Morgan was the inventor, but they STILL do it!

"An archaic sliding pillar front independent and live axle leaf spring rear suspension can provide surprisingly entertaining handling"

from:
http://www.autosite.com/buyersguide/2004-morgan-plus-8.asp

[jdstuff]

Charlie,
Akron placed #6, if you are just looking at the scores from the dynamic events. Fuel economy killed us in the endurance, so ignoring that we could have scored even higher. We run Goodyears 13x6.5

Also, the Goodyear rain tires are amazing. We got a chance to run an endurance with slicks and rains back to back (11 laps each) before comp this year. Lap times in standing water were VERY close to the dry times.....Kudos to Goodyear. Although as we found out after R&T, Goodyear rains don't make as much smoke as the Hoosiers when you are doing donuts...pity.

[Tidexcab99]

Charlie...I sent you a PM.

[RagingGrandpa]

Sliding Pillar Suspension = binds under side load http://fsae.com/groupee_common/emoticons/icon_frown.gif

[Tidexcab99]

Have any teams ever tried mixing halves and centers from different companies...Keizer halves with Kodiak or Weld centers??

[Angry Joe]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Beast:
Judges didn't seem to like our 10" wheels and neither did the Hoosier tire guy. Things like cost and weight when it came to tire selection didn't seem to matter. <HR></BLOCKQUOTE>

Hoosier can kiss my ass. When they finally decided they wanted to mount Lehigh's 10" tires they had no problem.

Pros of 10" wheels: less unsprung weight, less rotational inertia, much cheaper.

Cons: fewer tire choices, tougher to mount, much harder to package brakes and suspension geometry. I've heard people complain of poorer response and steering feedback but none of our drivers complained...

[Big Bird]

I wrote ages ago that I'd post some info on relative Moments of Inertia. We tested 2nd hand Hoosier 13x6's on 4mm thick 6061 rims (8.1kg w/centres), and new Goodyear 10x6.5's on 4mm thick Douglas rims (6.9kg with centres). The MoI of the Hoosiers 13's was 57% greater. And against the lightweight but concrete compound Dunlops we used at FSAE-A last year, (Douglas rims again) the 13" setup MoI was 75% greater. So even when weight difference isn't much, there is still significant rotational inertia difference. (Sorry, not posting exact results, I'm sure you all understand. I swear the values are correct though).

Tyre choice - well certainly there isn't as many to choose from with 10's. But its a pretty thin argument when the same brand and compound tyres that the top 13" teams are using are available in 10's anyway. Ditch that argument.

Geometry, brakes - yep, gotta consider that. But it isn't the issue that some people make it out to be. It's not as if you can't find a geometry that works. As for brakes, if F1's can get away with brakes inside 13 inch wheels then I think it a little ambitious for anyone to say their FSAE pocket rocket needs the same.

Poorer response? Steering feedback? Good grief, we are trying hard here. Face it, we are amateurs, most of our drivers couldn't really tell the difference anyway. A lot of us are probably still learning how to set corner weights properly, why sweat the little stuff? When M. Schumacher enrols at UoW, J.P.Montoya at UWA, K.Raikkonen at UTA and M.Webber signs up for a pottery class here at RMIT, that would be the time when we'd all have to start truly thinking about tiny degrees of steering response. And only after we got everything else right.

Getting back on track, I'm not going to say here and now that 10's are the only way to go, they are not. Nor are 13's a holy grail. Either will work. Get an overall concept in your head for your car and work it through, and don't sweat too much about what everyone else is doing. Build your car straight, get it running cleanly and reliably, set up corner weights and tyre pressures and go out there and drive the damn thing. You'll be streets ahead of all those who spend endless hours in design meetings conceiving the world's most ideal CAD model.

Crikey, I'm starting to sound like Angry Joe. All I need now is a gratuitious nasty word. Hmmm. Let me see. Bollocks. There you go, I feel much better...

Cheers,

[Charlie]

I disagree, I think that the fact that there are no professional drivers here makes steering feedback and driver feel much MORE important. You have to inspire confidence in your driver because he really doesn't know what he's doing. http://fsae.com/groupee_common/emoticons/icon_wink.gif

Can't comment on 10" vs. 13" by any direct comparisons though.

[Denny Trimble]

Geoff,
Thanks for sharing the inertia numbers. Do those take into account the rolling radius difference (squared)? An 18" OD wheel has to turn and accelerate faster than a 20".

[Charlie]

Anyone know offhand who ran 10s last year? I remember WWU and Lehigh. I did notice RIT ran 13s for what seems like the first time ever. And NC State was running 13s as well I beleive?

[Big Bird]

How you doing Charlie,

For what it is worth, none of our drivers have complained about lack of feel with the 10's, and in fact Rotor has commented that feedback is spot on as far as he is concerned. We can compare against our 2002 car with 13's and a CBR engine, but it is a bit of a moot point really. One day for a joke we'll put the 13's on the little single and see how it goes. That's if we can see over the top of the wheels.

The point I was trying to make re steering feedback is that for a new team, sweating over a personal preference like tyre feel is just adding another variable into what is already a mammoth task. It is one of those things that you can spend hours arguing about and when the car finally hits the track, there will be other things to contend with that will well and truly overwhelm any differences caused by a few mm of tyre contact patch here and there. If a car isn't set up properly with known ride heights, tyre pressures, corner weights, wheel alignments, cambers, front and rear toe-ins/outs, blah blah blah, then arguing about merits of different contact patch shapes or wall stiffnesses is a bit academic.

Of course, for a more seasoned team who has all the above under control, it is a different matter. Worry away!

I'm going to reconsider something I said earlier though. Given this thread is about first year team's tyre choices, then 13's probably would be the way to go. No point making life hard for yourself first up when you have all that other stuff to contend with. There is greater merit in getting a car running reliably and seeing out your first comp, than worrying about where you can save a kilo or two of unsprung weight.

Good luck Tidexcab99 with your first car. Have fun!

Cheers

[MikeWaggoner at UW]

It seems like most of the people I know that complained about 10" rim feel were driving them a few years ago, and hadn't driven on a car with reinforced 10" rims within recent history.

[Daves]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>And NC State was running 13s as well I beleive? <HR></BLOCKQUOTE>
N.C. State 2003: 10" wheels & tires
N.C. State 2004: 13" wheels & tires

[jack]

yes, WWU has allways run 10's in the past.

just for the record, as soon as i can afford some 13" rims, im getting rid of those crappy ten inch wheels forever.

[Beast]

Anyone run 13" and 10" wheels/tires on the same car yet?

Does anyone think making adapters to do this with a car that doesn't handle well (pushes like a mother), a good idea for making a decision between 10" and 13" wheels?

[Big Bird]

We are planning to run 13's on our car when we get it home from FStudent, so maybe September? Don't know what it will prove given that the geometry is set up for 10's, but we'll post whatever happens.

Cheers,

[NJM.]

We at NC State have run 10s and 13s on the same car. We have run 10s for the past few years until the team went to 13s this year. Over the summer of '03 we tested our 8th place finisher from 2003 with goodyear 10 x 8 and 13 x 6 in a few different compounds and on different wheel widths.

When we decided to run 10s so many years ago, you could save at leist 10 lbs a corner because of tire construction and wheel selection. Now the 13s tires and wheels are both built lighter so the gain is not worth as much especially if you build your own wheel centers.

Some benefits of the 10s are still lighter weight and lower cost. Some downfalls of 10s that we found were low wheel stiffness for available rims, VERY hard to mount tires (usually ruin a rim or two), tough to package acceptable susp. geometry (although not impossible)

Benefits of the 13s are greater availability (it may be tough to get 10s in the future), easier to package, wheel stiffness, ease of mounting tires, more options with susp geometry and brakes.


From a performance standpoint, i believe we had gotton the most out of our 10" tires in 2003. We finished 8th at comp and 8th in endurance with a flat LR tire for the entire second stint. Swithching to 13s with the same style, (ie not stiff) wheels not changing setup we had no significant drop off in performance. The tire wear and temps were similar between the two. I think there is no magic tire size. I dont think you can make a good car with 10s go faster than a good car with 13s or vice versa. If I were desiging a minimalist car, ie small motor etc. i would use 10s for the weight and the wheel stiffness would be less significant. Designing a "traditional" fsae car, 600cc motor etc. I would use 13s for their ease of use and need for wheel stiffness. If I were using 10s i would stock up before comp though.

On a related note, i dont believe wheel stiffness will give any more maximum grip only a better response to driver input. A non stiff wheel can be just as fast as a stiff wheel with a good driver. The camber loss due to wheel deflection is very small and with big sloppy bias ply tires and low air pressure it is negligible.

Good luck to those at FStudent. hope you get good weather.

-Noah

[HondaFan]

We have decided to use 10 inch wheels for our next car . have checked out the Keizers 10 inch 2 peice shells....they are cheap and light for our requirements.
Can anyone tell us what is the most suitable bolt circle Dia and Wheel offset for these wheels? Do they require stiffners?
We found that Atv Brakes will be the most approprite to fit inside these. Does any one know of any specific Brake caliper pacakge from an ATV which will be the best for this size.

Also is it a good idea to have the brakes behind the upright, that is between the A Arms.WE can have a Rotating spindle type of HUb with the wheel flange on one side and splined dog clutch type flange on the other to hold the rotor with enough OD to fit in between the Ar Arms OD and very small ID to jus fit on the spinfle end.? HAs anyone done this? I had seen brakes between the Rear A Arms on the Western Australia University Car? will there be any unwanted forces acting on the wheels during braking with this type of setup?

Abhinav Gaikwad
Team MHSSC Racing
INDIA

[exFSAE]

YOU need to decide bolt circle pattern and offset from your suspension requirements.

Having the brake rotor inboard of the upright is just fine though.

Why you using 10" wheels?

[Big Bird]

Agreed with exFSAE, you will need to sort out offsets etc according to your packaging requirements.

As for inboard rotors, I don't think it is a good idea with 10" wheels. Depending on your suspension geometry, your vertical seperation between balljoints at the upright will be significantly less than 10" (maybe 7"-8" or so), and then by the time you take into account the thickness of the A-arms and maybe some A-arm angle for camber gain you might only have 5" diameter available for your inboard disc.

It is hard work packaging everything inside a 10" wheel, you need to think your choice through very carefully.

[oz_olly]

Good to see you still dropping by Geoff. I was looking through some old pictures yesterday and saw the old RMIT Turbo car, how things have changed. There was a really tall guy standing around too http://fsae.com/groupee_common/emoticons/icon_razz.gif.

I am designing a front and rear beam axle suspension for our car this year. I chose to go to 10 inch wheels to help offset some of the increase in unsprung mass. I don't have a direct comparison between this set up and our previous years (double A Arm). In order to get the scrub radius I wanted with zero steering axis inclination I have done two things: designed a brake disc set up to go on the inboard side of the upright and designed a custom wheel centre with a large offset. The idea came to me once I chose beam axles. I started looking around on my daily drive to work looking for vehicles with beam axles. As most trucks have them I get excited if I am behind one in traffic as a check out the designs. I did notice that nearly all trucks have a front wheel offset so large that the wheel bolt flange extends past the outboard side of the tyre. I haven't quite gone to this extreme but it's in that direction. I have been able to package a 180mm dia brake disc with provision for camber adjustment and ackerman by parts substitution. It has been a nightmare of iterations to get it stressed and fitting within the required space. I also made a comprimise at 35 deg wheel steered angle.

I still agree with what Geoff has said earlier about brake discs on the inboard side with double a arm. I am sure it can be done but it wouldn't be quick or easy.

I am planning to freeze a lot of my designs this coming week so I will probably put a bunch of pictures on our website when finished.

Cheers

Olly
ACME Racing
UNSW@ADFA