mark kibort

The 928 has been just a dream of reliability and surprisingly fast. However, most of my competitors have all started to buy new tires and more often as well. My days of the dumbster diving are over. at best, i got a set from a record setting car after 5 heat cycles that would last me 3 weekends.... at worst, i got unknown set, like the time at Road America , where those tires run at thunderhill when i got back were a full (and im not exagerating) 3 seconds slower. So, i started this last season to buy a new set and only use them for the races, and after they start getting squirly, use them for practice and qualifying (if good enough) .
However, what happens , on a staggard rim set , the fronts wear out faster than the rears , by a factor of near 2 to 1. however, if i dismount and move the fronts to the rear and visa versa, i can get another couple of races out of them before they heat cycle out.


the problem is that the fenders up front dont allow for anything larger than how ive slightly modified the fenders. taking it a level further, i pulled the fenders from the chassis and it allowed me to at least run the same size tire front and rear 315x30x18.

after seeing the fender mods 10 years ago of a rennlister, I've made a decision to cut the fenders and create the space that will allow all the rims to be the same size and offset (8" backspacing , 11" width)

Here are the pics of that project that ill be starting as soon as i finish my wheel bearing issue.

thoughts?

I kind of like the fenders pulled out to have the active venting. very porsche 935-ish.

Mongo

I really like the look of those fenders and the more aggressive stance the front end has.

I am more curious to know about those 'fixed' headlights I see on that blue track car.

mark kibort

I know! also, those headlights are very interesting they look great and probably work well. who's car is this and what has it been up too!!???

dr bob

Doing a few "what-if's" for projectors headlights, adding them in that location means that the bottom of the dipped-beam pattern is blocked by the body and bumper height immediately forward of the headlight. It also puts the headlight below the 24" minimum for bulb center.

It does look cool in there behind the plain lens though. Just doesn't do much for you when driving at night.

mark kibort

actually, i had some lights in that same position. (square though) on a frame tied into the frame of the car. they worked great. the body didnt effect the short range lightening, however, they were rectangle vs these being round.

Mongo

Bob, Ken did something similar a long time ago I believe. I believe the consensus was the same about night driving. Nothing beats popups and that nostalgia of the 80s.

Snark Shark

If you vent it out the top, you could put some louvers there. Seems to be a common feature on race cars in recent years. Don't know what advantage they provide, but it sure looks cool.

mark kibort

aluminum 1/8" rivets? or steel? what is your recommendation folks

Imo000

Since steel rivets are stronger and this is a race car, go with steel.

Speedtoys

Steel for HP, Aluminum for TQ.

Mongo

I say you put some top vents on the fenders.

dr bob

Mark --

Will you ever be taking the rivets out? If so, go with aluminum rivets. 1/8" is too small. Use 5/32" or 3/16". All the vibration will load the area right around the rivets, work-hardening the fender metal there. The bigger rivets, with backing washers, are what you are looking for. Use the actual backing washers made for the rivets, not some hardware-store pieces. The holes are exactly the right size, and will keep the rivet from distorting and possibly tearing through your insert strips.

Reminder that all the fit-up is done with the Cleeco fasteners. Only put rivets in after everything is just right. Each time a hole has a pop-rivet set in it, the hole is stretched a little. Then it gets damaged again if you decide to drill out the rivet to redo something. Best to use the assembly fasteners as you do all your fit-up. Plus, do one side with the Clecos, then you can remove it and use it to template the other side.

Remind me how the front of the fender blends with the front bumper. Will you be widening the bumper shell too?

mark kibort

Thanks. Ill get the 5/32". i couldn't telll from the pictures what was used on the blue car. Yes, always use the spec backing washers!

as far as the front bumper, the beauty of this mod, is that the fender mounts at the front, do not change. the cuts are purely for athletics and to give the illusion of a equally spaced out fender, though its not. remember in my case, i dont need much room. its an inch wider rim to the outside , (im taking a 10" and making it a 11" rim with only the outer portion changed) but the same tire is being used, so i only need about a 1/2" more room to the outside.

dr bob

FIFY I think


If you really only need half an inch, I'd be working on the fender with a roller and maybe a hammer and dolly for the lip. NOT a baseball bat. The OC has a real fender roller in the toll loan program. Take advantage. Why do that instead of adding three or four extra inches to the width of the car? Drag from the increase in total frontal area. Your Cd number will go up as flow along the sides of the car is forced to separate at the rear edges of the fender, plus the frontal area goes up with the increase in width below the waistline.

mark kibort

Dr Bob, you might not understand how ive worked the fenders. these fenders are already massaged out an inch or so. the lip is completely flush on the inside and the aluminum has been slowly massaged to be pushed out as far as it will go without cracking. MOST folks have cracked fenders from being too aggressive, even with a roller system. my way, puts the bulge in where it needs to be , not oriented by a axis roller based system. this gives even MORE room. im putting an 11" rim and 315 tire, up front where normally, a 9.5" rim with 275 is pretty flush. i now run a 10" rim with a 315. so, lots of work, including slightly moving the fenders at teh bolts, AND the rear fender venting has allowed this. also keep in mind that the movement (position) of the lower rear fender mount has a HUGE effect on the shape and position of the fender near the tire. there is some radical position change, that ive worked with and is the key for making the fender pull out method work. (for example, if the rear lower fender attachment is disconnected, the entire fender falls on the outside tread of the tire, about .5" movement or more)

as far as Cd, this value is so insignificant overall, its hardly worth talking about. I dont have a value, but if i just take the increased value of the car, and increse the frontal area that i have increased the two sides, it goes up a fractional amount. Ive saved more drag with a wing gurney flap on the wing, than this mod will cost (for small wing angle settings) Plus, there are flow advantages, as well as increased downforce with the fender venting rear and upward.

pay close attention of how i flared the rear with form follows function, in only having the fender bulged where the tire moves, this can NOT happen by using a radiused based roller. lt works perfect and looks more clean as well, because the fender is only moved in places where it needs to be moved. (all with a baseball bat initially)

In fact, now aerodynamically, it is very clean with no airgaps for oncoming air to get trapped or hit flat surfaces. the transitions are vfery smooth as you can imagine by looking at the pics below.