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06-17-2019, 12:43 AM | #1 |
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Adding a 4 or 6 point harness to a Roadster - possible?
Hey Folks,
Did my first track days with my daily driven Z4M Roadster - absolutely loved it! Two minutes flat at The Ridge with tons of sloppy driving! I dislike the brakes, but can see a way through that with upgrades I've looked into. I absolutely hate being on a track with the stock seats and 3 point belts. I've tried researching options for mounting a harness, but end up getting lost in threads that look promising, but end up being coupes or cars with roll bars that are no longer daily drivers (or at least give up the soft top). I would prefer to keep the OEM seats, but am open to the possibility of a seat replacement. Any pointers would be much appreciated - cheers! Eamonn |
06-17-2019, 02:38 AM | #2 |
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Wow. Awesome time for first time out with the Z4MR at the Ridge.
How did the car feel to you? What wheel/tire setup are you running? Did you have DSC off? Great heel n toe down shifts. How did you mount your camera at that angle? It's great and I cannot get to that some how. Can you share? Not many of us track with a roadster. Roadster track-specifics are not very well documented. From my researches the last few years, I've leaning toward getting a bucket seat for track days. Have them off after the track for cruises is the preferred solution for me. A bucket with a 3 point will keep you more secured on the track than keep the OE seat and run harness and cut off parts of your interior. A bucket with less than 560mm in max shoulder width will clear the door panel without trimming. Once setup, getting the seat off are just few bolts. I think that's liveable. HTHs,
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06-17-2019, 10:51 AM | #3 | |
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Everything with a street/track car is unfortunately a compromise...
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06-17-2019, 03:16 PM | #4 |
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The car generally felt great except for the brakes. Good handling and balance, amazing mid-range grunt and top end power from the lovely S54 engine.
My past track experience is 90% with formula cars. I've never driven a street car on a track extensively (a few laps here and there). A single seater formula car brakes *way* differently than a road car hehe. I burned through a set of DS2500 fronts in 2 days. I am not sure what is wrong with my braking setup, but the pedal feel is terrible - long travel, soft through 80% of the travel, then form at the end; not at all confidence inspiring. And it does make heel 'n' toe downshifting much more difficult than it should be because of the radi ally different "bite height" for the brake pedal vs the gas pedal position. I bought it with 19" CSL knockoffs and some Hankook Ventus tires on the front, and General Tires on the rear. I swapped those out for 18" Apex ARC-8 and Michelin PSS 4 tires in a staggered setup. I left the DSC on. I will likely try it off once I get more comfortable. I kept forgetting to turn on the Sport button, but that seemed to help with throttle response. One day I will do an ECU hack to have that remember it's setting. I will find a pic of the camera setup - RAM suction cup mount on the rear console (the part that doesn't open). Very basic. Ran an external mic into the engine bay to get that amazing S54 sound You can kinda see the mount in this pic: https://photos.app.goo.gl/cfQBjDadr9tmRAv67 The 3 point seatbelt is problematic. At these speeds a 4 point harness seems like the only thing that will keep you firmly planted in the seat so you are not over exerting to brace yourself into position. The Bray Krause or Macht Schnell hardware and a seat swap (likely for the summer / season for me) with a competition seat seems like a good idea, but I would really like to have a 4 point or 6 point harness. I just can't figure out where to safely mount that shoulder straps? Seems like there are solutions for the lap belts and the ASM straps, but nothing I have seen for the shoulder straps that does not involve a roll cage. Thanks for the ideas and insights Gents! Cheers! Eamonn |
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06-17-2019, 03:33 PM | #5 |
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Re Belts - If you look at how Vanne has them mounted, this might work for you. I believe he is using eye bolts that are mounted in the rear bulk head. I also used a similar setup in my Toyota MR2. Keep in mind that most clubs will also require you to use a HANS device if you have a 4+ point harness; so bake that into your cost.
https://www.zpost.com/forums/showpos...&postcount=201 With regards to your brakes: Based on your last post, it seems like your using Hawk HPS street/track pads. Your description sounds like you have serious fade and are probably boiling your fluid. Definitely swap in a true track pad for your track days (like Hawk DTC60) and flush with any 600+ DOT4 Race Fluid and you should be good to go.
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2013 E92 M3 Competition 6MT Slick Top | AW / Fox Red | 2006 E86 M Coupe | Silver Gray / Imola | JRZ RSTWO | APR Aero | Sparco Seats/Belts | Weichers Cage Gone: 2017 Audi Q7 | 2011 E93 328i 6MT | 2014 Audi A6 | 2010 VW CC 2.0T | 2011 G37 S Coupe 6MT | 2004 G35 Coupe | SW20 MR2 Widebody Turbo |
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06-19-2019, 10:19 PM | #6 |
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Problem is even if you could retrofit a 4/6 point with proper harness bar, a lot of clubs still won’t let you run without a roll bar. And on a roadster that’s really tough...
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06-20-2019, 01:42 AM | #7 | |||
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Noted re: Hans, thanks. Quote:
I put in Castrol SRF fluid. I bled the brakes a couple of times at the track. The mechanic at the shop says the brakes were not bedded in properly and, as a result, this was causing the electronic braking system (??) to modulate the braking pressure. At least I think this is what he said, it kinda sounded odd to me, but he's a very experienced mechanic and has been spot on with other things, so - if that sounds weird - this is likely my lack of understanding of his explanation. In my view the brakes on the Z4M are the most inadequate aspect of the car. I plan to change out the front brake system, probably to an AP Racing PRO 5000 R based kit. Engine great, handling great, transmission ok, brakes are for a road car imo. Quote:
I made another lil video of me and my daughter out for a rip - slower lap times on purpose, but lots of fun https://www.youtube.com/watch?v=Dn3UeSqd5Gs Cheers! Eamonn |
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06-20-2019, 02:33 AM | #8 | |
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Just curious which clubs allow harnesses with bucket seats and no roll bar in a vert? If they have a regional chapter near me I’ll have to take a look as that’s the only reason that’s prevented me from going that route. |
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06-20-2019, 08:27 AM | #9 | |
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According to Ferdo's website, these 2500 pads fall off a cliff and begin to lose their coefficient of friction at 350* C / 650*F. You need to be using something like the 3.12 or Hawk DTC60/70 that maintains a stable and much higher level of friction all the way to 800*C/1500*F. Never used Ferdo which is why I keep drawing comparisons to Hawk, but the data they provide here seems pretty helpful. https://www.ferodoracing.com/product...e-pads/ds3-12/ Keep us posted!
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1995 E36 M3 | BMW CCA Club Racer - IP #34 | Gray / Blue / Orange | 261WHP | 2,700lbs
2013 E92 M3 Competition 6MT Slick Top | AW / Fox Red | 2006 E86 M Coupe | Silver Gray / Imola | JRZ RSTWO | APR Aero | Sparco Seats/Belts | Weichers Cage Gone: 2017 Audi Q7 | 2011 E93 328i 6MT | 2014 Audi A6 | 2010 VW CC 2.0T | 2011 G37 S Coupe 6MT | 2004 G35 Coupe | SW20 MR2 Widebody Turbo |
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06-20-2019, 11:18 AM | #10 | ||
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These are pretty informal groups, the most organized would be Hooked on Driving. They have a published policy on convertibles. Quote:
In terms of pads, I will likely try some DS1.11. And I need to get used to changing pads regularly (to swap from track / road pads). So much fun in this car, hoping to get back at it this weekend, but my cooling fan died and I need to get a new one in =/ Cheers, Eamonn |
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06-20-2019, 03:40 PM | #11 |
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Plenty of track groups would permit running a convertible without a rollbar, basically, once you sign the wavier you really are on your own.
For running my Z4MR on the track, I am leaving everything stock, and just use like CG locks or the old autocross trick to lock myself in place. Stock works and is tested, either you have a custom rollbar made, mount a proper 5-6 point harness and a proper FIA race seat in the car, or leave it stock. Personally safety is a do none or do them all sorta deal. DS2500 is a dual purpose pad, a good dual purpose pad, but still not a proper track pads. Just remember, the more capable the brake pads are, the faster the pad eat rotors, and the more corrosive and dusty brake dust comes out.
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06-20-2019, 07:09 PM | #12 |
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I think I will try some Ferodo DS1.11 pads on the front and 2500s on the rear. I will swap out the DS1.11s for some 2500s as my street pads.
I'm gonna use the 2500s as street pads so that in the event I need trackable pads in a pinch they will work. I am also thinking of doing a seat, harness, HANS device and mounting the harness the way Vanne has his mounted (as per the linked thread above). The CG Locks are interesting, I will try one of those out, if I don't like it, I can use it in the passenger seat for when wife and kids come along for a ride Cheers, Eamonn |
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06-20-2019, 09:01 PM | #13 | |
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As for smaller organizations (advanced only or open track days), I’ve actually found the rules to be even more strict. Not saying the above is absolute but in the northeast it’s usually more often the case you’d fail tech if you showed up with 5/6 points and harness bar only. Auto-x is an entirely different story... |
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06-21-2019, 09:37 AM | #14 | |
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Sadly with the Z4MR, it leaves many of us with very few options for safety, only reliance I have is to just run stock belts and believe BMW did their testing to ensure that if a tire fails on the track, I'll still be in one piece and the stock bar will hold me up long enough for me to crawl out. I stand by my view though, with any car the owner wants to make safe for track, do it all, or do none at all.
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06-21-2019, 10:17 AM | #15 |
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Rollbar and harness installed, the owner said it still allows the top to go fully up and down.
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06-21-2019, 09:55 PM | #16 | |
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The CG lock will go a long way to addressing your issue with being stable in the seat. I've used it for years for autocross and track and it makes a huge difference. Cinch it down till it almost squeezes out a little bit of pee-pee and you'll feel fine once you get out on the track.
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06-22-2019, 01:49 AM | #17 | |||
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If I can track down some info on the rollbar that allows use of the soft top and the price is reasonable I'd be quite happy =) Cheers! Eamonn |
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06-30-2019, 09:21 AM | #18 |
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My take on the whole thing is regardless of the rules, youd have to ask yourself a question. Is it a good idea to run 4/6 points with out a roll bar, pretty sure the answer to that is a definite no.
Same goes for the HANS device, can you run without it? Sure, but is it a good idea? Again, answer to that is probably no. Mod it fer sure, but do it safely. Eamonn, if needed mate, I can send you pics of how I went about it, I'll need to dig em up or take some new ones. Car is under 3 tarps ATM, hiding from the heat/sunlight. |
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06-30-2019, 11:28 AM | #19 |
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This thread has got me thinking if our factory roll hoops could serve as a roll bar that's required for harnesses but maybe the trick is to run non-fixed back seats. In that case maybe I can run a Profi II ASM FE's (DOT legal, anti-submarining tech, HANS compatible) with seats similar to this owner.
And then use eye bolt back plates welded to bulkhead, nice and clean like this. Entire setup is basically 95% reversible, not too crazy of hit on wallet doesn't appear to compromise safety. I may reach out to HMS to get their take... Last edited by 3002 tii; 06-30-2019 at 11:59 AM.. |
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06-30-2019, 12:50 PM | #20 | ||||
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It seems to me that if you are going over, the type of seat or seat belt has nothing to do with safety, it's over to physics and geometry that would be constant regardless of seat or harness type. Quote:
I will probably end up putting a roll bar into this car, but I need to do more research on a roll bar configuration that preserves the soft top. Based on the earlier post in this thread it can be done! Have reached out to that owner through the interwebz, but no response just yet. Quote:
In the linked thread above, the angle on the shoulder straps would not conform to best practices for mounting a harness. The shoulder straps should be flat, or angled down up to 25 degrees, but not angled up. The seats in the M - lovely for spirited road driving - are not usable with a harness because of the fixed headrest (and they do not have a hole for anti-sub straps, so afaik can only be used safely with the Schroth ASM capable 4 point belts). However, they should still follow the guidelines for mounting positions and angles. I notice the owner of that car said he would use the 4 point harness for Autocross, and the 3 point belt for track and daily driving. Not sure I understand why unless it's a governing body / approval issue. Quote:
This is what I am planning to do, and appears to be how Vanne mounted his shoulder straps behind the fixed back racing seat. I just ordered the parts for this from HMS. I am going to use a "proper" race seat - a Sparco QRT Performance - and a Schroth 6 point harness with Brey Krause mounting hardware and mount the shoulder straps into the rear bulkhead with Schroth FIA approved re-enforcing plates on the back side. I will mount these in a way that conforms to harness mounting guidelines. I believe this should be as safe as any roadster with factory roll hoops, and should provide a much better seating arrangement for track driving (which I could argue improves safety). Totally open to the idea that I may be missing something, this is safety so I am not wanting to mess about, but I can't get a roll bar into the car yet. However, I don't see the relationship between racing seats, 6 point harnesses, and factory roll hoops being less safe than factory seats, 3 point belts, and factory roll hoops. Cheers, Eamonn |
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06-30-2019, 07:18 PM | #21 | |
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And regarding the link I posted, I was not suggesting by any means that's a good setup. I was merely showing you the seat I was considering since the fitment was spot on. Therefore I posted the picture of the eyebolts showing how I would address the deficiencies in that other setup. Regarding fixed vs reclining, fixed back seats have high side bolsters so it's not meant to be used in conjunction with a factory 3-point setup as the lap belt would never get tight around your legs. For a track-only car ditching the 3-points is fine but strapping into a 5/6-point every time you're on public roads can be a hassle. Yes you can retain the factory 3 points but you still have the issue of the lap belts not securing you. Personal preference but not something I want to deal with (read not a safety decision but matter of convenience for me). Reclining seats don't have this issue but most reclining seats also don't have the hole on the seat bottom to run a 5/6 point, usually limited to 4-points. 4-points are generally at disadvantage because you run risk of submarining so that's why they're only allowed at low speed events like auto-x, unless you find a harness that has anti-submarining (ASM) tech. The harness I linked not only has ASM features but is compatible with HANS and both FIA / FMVSS 209 certified (so should be good for road courses). Separately during rollover, [the theory is] a fixed back seat will not give meaning the driver will stay upright if secured via harness. That's why a roll bar is crucial since you don't want the roof to collapse on you. Ironically if what I'm contemplating above "works", roadster owners wouldn't have to worry about this as the roll hoops would suffice for rollover protection. FYI I am by no means a safety expert so you should do your own due diligence but this is what I gathered when I researched the issue for my previous track car (and ultimately settled on "half" cage, fixed back and 6 points with HANS). So to recap, for my proposed setup, I *think* it checks all the boxes with respect to "street friendly", ASM, HANS, and rollover protection. A fixed back, aftermarket rollbar and 6 points would probably be safer but its not the direction I want to take the car in. Been there done that and I'm looking for something milder, easier on my wallet, and street friendly. Picture below is my old coupe for reference... Last edited by 3002 tii; 07-01-2019 at 09:54 AM.. |
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06-30-2019, 08:04 PM | #22 |
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Much more clear - excellent reply - thanks. Apologies if my written form tones as dickhead, your thoughtful response is much appreciated. Keep us posted on how you go, I will make an effort to do same.
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