Bump Stop Clearance

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JT68
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Re: Bump Stop Clearance

Post by JT68 »

After looking at this thread again, I think I see where the confusion originated...

The Nissan comp bumpstop was always intended for use with the original Datsun comp springs which are a bit taller than the supercomp.

I'm not aware of ANY expert recommendations to cut down the COMP bumpstops which are noticeably shorter AND already harder than the OEM stop.

The Bob Sharp bumpstop modifications were specifically for the OEM stop.

If you cut down the COMP stop significantly, you have eliminated 1/2 of it's usable elasticity and functional travel. That's a poor plan and a band-aid for the problem.

Hope this clears things up!
LT/JT
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Re: Bump Stop Clearance

Post by Datsunparts.comInc »

After finishing my long day I would have to look at this. Since you never made this part I will share with you the process I went through. I had these replica short bump stops made and not in any Chinese factory by the way. They are made here in the United States. During the process of having them made the company I worked with reverse engineered from a new Nissan comp set and also a new stock set acquired from Rallye. I had the durometer of the material checked and they are the same, albeit one being shorter. By the way, used original 50 year old tall bump stops are hard as a rock from age. Harder then my new ones. The reason why Nissan made the short bump stops later on was, at the time of Bob Sharp there was no alternative bump stop, you had to cut down the stock ones.
You do not have to remove a significant amount of material from the short bump stop to provide the proper clearance when using my springs and I have no expert recommendations I can point to that shortening them will cause a "loss of 1/2 usable elasticity"...... big words.
Try making the part first and then put it through rounds of testing before you theorize about design modification and parameters.
One of your own customers, after using the Mike Young springs he bought from you and later comp bump stops that he bought from me, had only 1/2 inch of clearance between the top of the comp bump stop and the bottom of the upper control arm with your springs installed. You advised him to cut more off the top of the comp bump stop, to effectively increase the clearance to 1 inch. He called me to ask if it was ok to grind them and I said "Jim is right you need more clearance". Good boy I'm right with you. I will have your customer forward the email you sent to him to me so I can publish it here if you want. For me the matter is closed.

D-
Last edited by Datsunparts.comInc on Wed May 05, 2021 3:31 am, edited 2 times in total.
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Re: Bump Stop Clearance

Post by Datsunparts.comInc »

theunz wrote: Tue May 04, 2021 5:39 pm Thanks Dean, that explains a lot. I guess I didn’t read the instructions or thought it was for OEM bump stops. I’ll check your web site and cut my bump stops. It should make those big dips and bumps in the road a little more bearable😁

When I was in school my progress reports usually had a check mark in the “usually does not” box for the “listens to and follows directions well” category🤔
Ha. That's funny. I remember that from grade school.
Yes if you don't provide the clearance you will have harshness. I have people throwing the instructions away all the time. Can you send me your email and customer name? Pm if you want I will send them to you. if you want the spacer for the lower spring that I have and that Rallye also carries I can send it you no charge like it says in the instruction sheet. Just advise by return.

D-
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JT68
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Re: Bump Stop Clearance

Post by JT68 »

I agree, bumpstop clearance should always be checked, we typically recommend cutting the OEM stops (which in truth are nearly always usable or easily replaced). The comp part was intended for track use, so we don't typically recommend them.

That being said, paying someone to draw up a part (any part), pasting it on a webpage and sending one away - saying "copy this for me", isn't engineering and never will be.

The recommendation to further cut away the comp bump is clearly based on zero engineering, controlled testing, or suspension design understanding. Not even a basic understanding of oversteer/understeer - it’s quite literally a hack(saw) to provide clearance for springs that are so short and stiff they introduce a host of problems.

That is why so many supercomps have been replaced with Mike's springs. (at least 25-35% of the sets we have sold).

I'm pretty sure someone thought: if low is good, lower must be better. But that isn't so. We've all seen ultra low Honda's bouncing around absurdly on the highways. I'm guessing those were "designed" using the same level of "engineering".

We introduced the Bilsteins specifically calibrated for the super comps to further help out with the problems- and they are very effective because they were specifically engineered for the spring rate and loading.

Anyone who is not sure about all the discussion in the thread can ask Mike too. He provides recommendations you can trust to hundreds of customers-and always has! Anyone who drives on the Mike Young springs and Bilsteins will tell you as well.
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theunz
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Re: Bump Stop Clearance

Post by theunz »

Thank you Dean, that is very generous of you, I’ll send a PM
Mike M

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Re: Bump Stop Clearance

Post by Datsunparts.comInc »

As you say "zero engineering, controlled testing, or suspension design understanding" And you did controlled testing done independently through a company that does this kind of work! I think not. Let's leave that at the side of the road.
The company I used has engineers that build suspension related parts and they made recommendations.
The Datsun comp springs and bump stops were available through Datsun comp. You say meant only for racing or track purposes.
Wrong. Get your history straight. Datsun comp always represented themselves as selling race only items and that is why they offered no warranties.
That didn't stop many people from buying parts from them to use on street vehicles. Tons of people used Datsun comp springs on the street, before any of our springs were available. The Datsun comp springs are only 3/16" higher than yours and people used the short comp bump stops Nissan sold and every vendor that had an account used to sell them on this forum.
Your friend Don Morrell sells some CAG version of the short bump stops. So 3/16" is nothing and would not prohibit use of the comp bump stop with the Bob Sharp modification which, when done on a tall bump stop, works nearly out to the same as the short bump stop and use it with the MY spring.
So throw another Nissan part they had made and designed under the bus, like Nissan's U20 water pumps and any other fanciful thing you like.
You do that well and it serves you.

D-
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Re: Bump Stop Clearance

Post by todd lorber »

So...NOW is the matter closed?
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Re: Bump Stop Clearance

Post by Datsunparts.comInc »

Jesus hopefully, but you never know with jt
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Re: Bump Stop Clearance

Post by JT68 »

todd lorber wrote: Wed May 05, 2021 3:43 pm So...NOW is the matter closed?
I guess like Tom Petty said "you believe what you want to believe" or in this case "who" you want to believe. I'm calling BS-again-and numerous experiences on 311s support that.

Yes, some comp parts are totally appropriate for street use (like the front springs and mikunis) others are really terrible (like the comp rear springs, camshafts or 13:1 pistons)-the key is understanding what works well together as a system and why.

We prefer cutting the stock bump stop as Bob Sharp suggested for improved street instead of comp front stops. Why? because the comp stops come on too hard. Couple that with an overly stiff spring and you get a ride like a delivery truck.

I don't know of any complaints EVER with the Mike Young springs, there are plenty of threads on 311's about problems with the springs discussed in this thread. I guess that famous, secret "company that made the recommendations" didn't actually know too much about Datsun roadsters...

Please note, No personal criticism of Dean, he is just a salesman, not an engineer. I don't expect him to understand engineering, engineering principles, mechanical or electrical technology.

I'm always available to discuss roadster tech, engine builds, suspensions or automotive engineering for further insight!
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Re: Bump Stop Clearance

Post by rwmann »

Bump…
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theunz
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Re: Bump Stop Clearance

Post by theunz »

The following is a copy of a PM that I just sent to Dean. As I was writing it I decided that I should post it here as well. We have several excellent vendors, but both Dean and Jim have been instrumental in producing rare and unobtainable parts. I hope this helps put the water under the bridge.

Good grief, I was just wondering if perhaps I had done something wrong and it turns out that I had by not cutting the bump stops. I didn’t mean to open Pandora’s Box! It’s a shame to see Jim attack your parts, and I don’t blame you for defending yourself. Like yourself, Jim has developed some great parts for our cars, however if he feels that something he sells is superior to another vendors he should tout the attributes of his product, not disparage the competitors part.
Although I have purchased the vast majority of my parts from you, I have also bought from Jim, Stan, Paul and others. I believe that all have been a great service to the roadster community and wish all would respect one another. I am thankful that we are blessed with so many options for part sources to support such a niche vechicle.
Mike M

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1969 2000 solex mine since 1972, under resurrection. (Finally resurrected as of spring 2019!) 1969 Porsche 911s -worth more, but not as valuable!
JT68
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Re: Bump Stop Clearance

Post by JT68 »

Mike, the question and thread became more complex, as these threads often do, when the question was posed about omitting the bump stops all together and the significant danger that would create. That required clarification.

Cutting the bump stop too low is also a bad solution and doesn’t address the root cause of the problem shown in the original post.

I give you that assessment based on owning, building AND DRIVING roadsters for40 years, ME/EE engineering degrees and 38 years of engineer career. Add our other ME and it’s 78years of engineering in house. Plenty of root cause analysis in all those years.

What I did primarily was strongly recommend Mike Young springs and recommend cutting the bump stops per the Bob Sharp recommendations-that is a bulletproof recommendation, so I stand by that. It will greatly improve the ride and handling-ask anyone that has them.

I don’t need to bash the supercomp springs or the comp bushings, again just read the countless 311 posts. It is clear which is the superior product, no matter who has a tantrum about it. The Mike Young springs were not developed by me, so they stand on their own merit.

If you prefer to believe Dean's vast technical expertise and engineering assessment, that is your call. Others are free to choose.
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Re: Bump Stop Clearance

Post by unklpat »

As someone who doesn't shy away from confrontation, let me add my opinion. Dean and Jim both offer great products for our cars. Dean, your stainless flex lines, and reproduction trim for our cars rock! Jim, your shocks and adjustable timing gear are great! However, if I was a new roadster owner, would I want to order from someone who bashes their competition? Not likely. In one of My prior careers, we had to have hard facts to put against our competitors, or risk litigation, no such hard facts exist here, only heresay, and ego.
I would ask each of you to pretend you are a new roadster owner, and happened upon this thread. What would you think? Do you see Paul wells, or Don at rising sun, or sin city, or new datsun parts, or the others chiming in? No, because they know this is not the way to increase business, only the way to fracture a community built around these cars. I've only had mine a couple years, but have immersed myself in making it the best it can be. I've learned a lot,ordered from all of you, and one thing I've learned, is that you don't need to build yourself up if you have good products and service.
Dean, and Jim, please stop bashing each other. It will not help your bottom line, only make each of you look small. You are both great resources to us.You should , as should all vendors, feel good about that. Pat