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Bump stop box query

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warwick-steve

warwick-steve

Jedi Hopeful
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Hi all
Does anybody know the recommended gap distance between the underside of the bump stop box and the top of the bump rubber on a BT7. I am replacing the old rusty boxes and will have to modify the new ones to fit. ( The old ones were also modified by reducing the depth of the box).
Thanks
Steve
 
Steve, I'm really curious now, why do they have to be modified? When I replaced the ones on my BJ7 they just bolted in.
 
I would think that the only reason you'd need to modify these boxes is if your springs are shot and saggy. Have you thought about that?
 
Hi, thanks for replying
I do suspect the springs as it does sit a little low ( gap between top of wheel and wheel arch) however it rides really well with no bangs or squeaks. A local Healey specialist who looked over the car some months back didn't think this excessive and did not consider it worth changing the springs yet.
The car was completely restored in 2010 - 15000 miles ago by a respected Healey restorer. What surprises me is that he would have modified the boxes. ( Ican't check with him as he is very ill). I don't think the springs were new but I find it difficult to believe he would have used springs that were "shot".He did use a new chassis, rear wings and I suspect inner wings as well.The shock absorbers are new.
I wondered if he positioned the bump box bolt holes too high. -- It would be useful to know what the distance from the bolt holes to the underside of the inner wheel arch, where the box fits, should be.
Thanks for your input, any further comments would be appreciated
Cheers
Steve
 
Pretty sure my car has only 2 to 3 inches between the bump rubber and the stop. It's got new springs. . When I got it one damper had sheared its shaft , on that side the bump box had been punched upwards damaging the rear seat pan support area. If it hits the stops too often when it's back on the road I will simply cut down the bump box rather than the rubber. I do think there might be two rubber heights though. ?
 
warwick-steve said:
Hi, thanks for replying
I do suspect the springs as it does sit a little low ( gap between top of wheel and wheel arch) however it rides really well with no bangs or squeaks. A local Healey specialist who looked over the car some months back didn't think this excessive and did not consider it worth changing the springs yet.
The car was completely restored in 2010 - 15000 miles ago by a respected Healey restorer. What surprises me is that he would have modified the boxes. ( I can't check with him as he is very ill). I don't think the springs were new but I find it difficult to believe he would have used springs that were "shot".He did use a new chassis, rear wings and I suspect inner wings as well.The shock absorbers are new.
I wondered if he positioned the bump box bolt holes too high. -- It would be useful to know what the distance from the bolt holes to the underside of the inner wheel arch, where the box fits, should be.
Thanks for your input, any further comments would be appreciated
Cheers
Steve
Click to expand...

Steve,

My BN6 is assembled and sitting on jack stands installed under the frame, no engine or gearbox installed. The rear differential carrier is resting on the rubber frame pads. The distance between the top of the original cone shaped rubber bumper and the bottom of the original metal bump box is about 4.5 inches. My springs are original, pictures below.

I hope this helps!

Edit: Also, Steve posted this a while back, it shows the distance while racing.

https://www.britishcarforum.com/bcf/showthread.php?96412-Dutch-axle-windup-video




bump1.jpg


bump2.jpg


bump3.jpg


bump6.jpg
 
Last edited:
Duane - those look like BN4 brake drums. My old drums have ribs around the circumference.

You'd have to support the car under the axles to show the true distance between the conical bumpers and the bump boxes.
 
steveg said:
Duane - those look like BN4 brake drums. My old drums have ribs around the circumference.

You'd have to support the car under the axles to show the true distance between the conical bumpers and the bump boxes.
Click to expand...

Steve,

Yes, my BN6 came with the disc wheel drums shown in the picture when I bought it back in 1976!

You are correct, once the car is on the ground, the distance between the conical bumper and the bump box will definitely be less!

Thanks,
Duane
 
Thanks everyone
That is a great help. I think that the bolt holes are positioned too high on my car. - Duane, would you please be able to let me know the distance from the bolt centre line to underside of the arch where the bump box flange is fixed? This would help confirm my suspicion.
I am pretty sure the restorer used new inner panels as there are also no seat belt fixings as there should be on a 1961 BT7
Thanks
Steve
 
warwick-steve said:
Thanks everyone
That is a great help. I think that the bolt holes are positioned too high on my car. - Duane, would you please be able to let me know the distance from the bolt centre line to underside of the arch where the bump box flange is fixed? This would help confirm my suspicion.
I am pretty sure the restorer used new inner panels as there are also no seat belt fixings as there should be on a 1961 BT7
Thanks
Steve
Click to expand...

Steve,

I think this is the dimension you're asking for. If not let me know!

Thanks,
Duane



Dimensions.jpg
 
Looks like the same boxes as on the BN1. Why do they have holes in the side? Are they manufactured wrong? Should the holes be in the bottom? I had to add holes in the bottom for drainage otherwise they will fill with water.
 
Am I missing something? The boxes are affixed to the frame with bolts through the holes on the side. The boxes are 5-sided; i.e. they are open at the top of the 'box' part. If they were bolted through the bottom, you'd need 3+ inch bolts.

If you run wider-than-stock wheels and/or tires, the tires may rub against the bolts during hard cornering (at least on a BJ8, where the axle rides lower). The boxes on both my BN2 and BJ8 are bolted the other way; i.e. with the bolt heads on the outside instead of the nuts with lock washers as shown in the photo. I think the rubbing could be worse--potentially catastrophic--with the arrangement shown (I'm seeing fairly sharp half-a-thread or so on both bolts). I'm considering grinding the bolt heads down so there's less chance of rubbing with my 6" rims and 185/70 tires. Also, the first time you hit a nasty railroad crossing or serious pothole the boxes will assume a less-than-squareish shape.
 
Bob_Spidell said:
my BN2 and BJ8 are bolted the other way; i.e. with the bolt heads on the outside instead of the nuts with lock washers as shown in the photo.
Click to expand...
Same with my original bolts. The heads are in the wheel well. I think the nuts were welded to the wheel well inside the cockpit.
 
Not sure how the 100's were done but my BT7 came with the bolt heads on the inside of the car and the washer/nut on in the fender well like Duane's photo.
Intherestingly, Sports and Classics web site has a photo in their upholstery section of a 3000 roadster with these bolt heads showing, but they penetrate the side panel about 6" higher than mine. It's the white interior with red piping. Not sure why.
 
FWIW, the Moss catalog shows the BJ8 with the bolt heads in the wheel well; all others with the bolt heads in the interior. The pictures in Anderson Moment seem to show phillips screw heads in the interiors.
 
I think having the heads in the interior would be more comfortable on the hips than the nuts, not that those tractor seats are all that comfortable.
 
Just to add to the mix, on my 1961 BT7 (currently undergoing restoration) the horizontal hex head screws (as per above pictures) had the screw head in the wheel well and the nut (captive / welded) on the inside. The length of the screw meant little showed past the nut. On the vertical screws, these were pan head, with the head inside the car and the nut underneath in the wheel well, but out of harms way.
 
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