New Bump Stops

Technical and Repair Discussions
User avatar
Ready to Write a Book
Ready to Write a Book
Posts: 56
Joined: Sun Jul 06, 2014 11:14 pm
Location: Los Gatos, California
Chassis:
281
Facebook Page:
https://www.facebook.com/Accelracetek-285423508982
PostPosted: Mon Jul 15, 2019 1:32 am
New shock bump stops are now available. These are custom designed by SCCA-E for the SpecRacer and are replacements for the Penske stops. They are optional for this year. The new stops seem to perform for most track conditions. Next year you will need to run these or no stops. The stops are available from you CSR or can be purchased online at http://www.accelracetek.com
Attachments
SCCA SRF Bump Stop LR.jpg
SCCA SRF Bump Stop LR.jpg (19.1 KiB) Viewed 4191 times
User avatar
Needs a Life!!!
Needs a Life!!!
Posts: 735
Joined: Wed Nov 30, 2011 12:21 am

Chassis:
595
PostPosted: Mon Jul 15, 2019 2:34 pm
The existing rules allow the bump stop to be shortened. Will this be allowed with these as well? They look rather long when I saw them installed on a car last weekend at Sonoma and I expect they will compress under load (though they appear much softer than the original Penske bump stops), though I didn't hear any complaints about handling, which was a big issue in the past at this track with the original Penske bump stops, which would create some pretty exciting moments under load in T1!
Bob Breton - SRF 51 - San Francisco Region
User avatar
Needs a Life!!!
Needs a Life!!!
Posts: 752
Joined: Wed Nov 30, 2011 1:03 am

Chassis:
828
Facebook Page:
http://www.facebook.com/#!/denny.stripling
PostPosted: Thu Jul 18, 2019 11:04 am
They are about 3/4 the length of a full Penske, and probably close to twice as stiff.
____________
Bay 12, please.

Ready to Write a Book
Ready to Write a Book
Posts: 92
Joined: Fri Apr 22, 2016 5:11 pm
PostPosted: Sun Apr 19, 2020 8:13 am
I installed a set of the bump stops (4). I then read Mike's memo testing the four varieties of bump stops. If I had known the rule and read the tech bulletin first, I may have gone without bump stops.

The new bump stops are short (2") and firm, and based on Mike's memo unlikely to come into play on most tracks because at legal+ ride heights you just don't use that much suspension travel. Mike's bulletin says that you could remove the bump stops on a rough track. So why have them at all?

PS: The SCCA bump stop slides freely on the shaft, so it sits on top of the shock body, not up at the top of the shaft. Is that a concern?
Last edited by Greg-Cirillo on Mon Apr 20, 2020 4:08 pm, edited 1 time in total.
User avatar
Needs a Life!!!
Needs a Life!!!
Posts: 735
Joined: Wed Nov 30, 2011 12:21 am

Chassis:
595
PostPosted: Sun Apr 19, 2020 1:03 pm
So I went through the PIA process to remove the old Penske bump stops before I ran at Sonoma Raceway in February. I decided to see how it would be to run without putting in the bump stops. As many may recall, we learned quite early on that the full length original bump stops would bottom out very easily, creating some pretty "interesting" car behavior, especially at high G force tracks like Sonoma (Sears Point), up the hills in T1 and T3, so cutting them in half (or more) was SOP.

The behavior without any bump stops was a non-event. No sudden twitches or sensations of bottoming. I tend to use some of the curbs, though T2 is the only really high curb at the apex. I have a short video of the last 4 laps at Sonoma and, while the car was definitely "edgy", a lot that can be placed on the significant headwinds down the front and tail winds heading down the back section, which made for some fairly unpredictable handling changes (none that I would attest to running without bump stops.) https://vimeo.com/406898723

At this point, I plan to continue (hopefully) to run without the new bump stops. Laguna Seca will be a good test as we have some very high G sections that also can bottom out the suspension travel, especially at the bottom of the corkscrew, and the "hold your breath" middle of T9. Just seems like a lot of money to spend for no particular purpose. I suspect the rule change was primarily driven by "revenue enhancement" and nothing that justifies "outlawing" the current bump stops. That's progress I guess... ;-)
Bob Breton - SRF 51 - San Francisco Region

Ready to Write a Book
Ready to Write a Book
Posts: 92
Joined: Fri Apr 22, 2016 5:11 pm
PostPosted: Mon Apr 20, 2020 7:46 am
I suppose that the bump stop protects the shock at the end of its range (if your springs somehow allow that degree of travel - an addition 2"), and the new SCCA bump stop is the shortest so least likely to come into play. Maybe I'm wrong, but maybe the right move is to just run no bump stops.
Last edited by Greg-Cirillo on Mon Apr 20, 2020 4:09 pm, edited 1 time in total.
User avatar
Ready to Write a Book
Ready to Write a Book
Posts: 93
Joined: Sun Dec 04, 2011 6:46 pm
Location: Windham, NH
Chassis:
492
PostPosted: Mon Apr 20, 2020 2:33 pm
I'm interested to hear from others. I too have purchased these, but have not installed them. Does anyone have any feedback why we would need them?
Steve Introne
NER #12
Nat F&C

Return to Technical and Repair Discussions

Who is online

Users browsing this forum: No registered users and 4 guests