Spring rate

Burris Racer

Burris Racer

Member
I’m looking for some help on spring rate testing. I have access to a digital Intercomp testing machine. The instructions I was given are to jack the table until the gauge reads 10, zero out the caliper, jack the table 1/4”, wait 3 minutes, and then move to 3/8”, wait at least 3 minutes and record the number on the gauge. Does this process sound correct?

The next question is how do I use this data? Say I have 1 RS tire that reads 115 and the other RS reads 105. 1st question is what variance is a measurable difference. 2nd question is where would I want to place the higher spring rate? 3rd question is how do I use spring rate and durometer (ie 2 sets of tires have the same spring rate but are 8 points different in duro or 2 sets have the same duro but are 10 points different in spring rate)?
 
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I believe you want to match the tires up by spring rate .
Something tells me they should be matched before prepping .
Will be interesting to hear what the tire guys say .
 
Here we go again....
The spring rate you test in a controlled environment will be different on the kart in race conditions , and tires rates wont change uniformly while racing, too may factors...ambient temp, track temp, air pressure, tire prep used.
Match the type/brand by duro and dont worry about the spring rate.
Another tool we sold at a loss
 
I don't know...
I guess I'll disagree with Jamie again on usefulness of tools.

Burris tires are all over the place on spring rates, even within the same production codes.
While Jamie is absolutely correct in his assertion that the spring pressures vary while on the track, (absolutely they do,) I find it an advantage to know what you are starting with.

We match our tire sets by date code first, then by spring rates. We are primarily interested in right sides matching. I don't even bother with lefts any more. About the only time we check left rears is when we want a stiffer left rear for high cross on big momentum tracks.

Keep in mind that cutting/profiling the shoulder makes a BIG difference in spring rates on a soft sidewall tires, 33s in particular, (not as much on Maxxis, Cobra, Hoosier FK & A40, or Vega Yellow & Blues.)
Most of our 33 stuff doesn't get internally prepped so we don't have to worry about that changing the spring rates. Now, for some of our short track 33 tires that have internal, you can bet that the sidewalls are affected.

Now, consider that you're at a Burris 33 only track: If it's a big momentum track, why would you not want the highest spring rate tires on your kart? It sure beats running higher psi and having to add more prep to get the tire to grip in the corners.
Higher spring rates = roll speed without having to jack the air psi way up.
I find roll speed to ALWAYS be an advantage. That advantage is most easily seen on big momentum tracks, or tracks that bite up good.

It's kind of like the tire temp discussion in another thread on here...
Over emphasis on any one point of data can be misleading. The whole package that has to work together in harmony.

----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
31 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
average kart racers arent checking 100's of tire, cant pick the cream of the crop, they are forced to work with what they have purchased locally/online/used.
For burris, guys will prep them 4 of 5 different ways because they are limited on what they have, thus changing the side wall.
Ambient temp of the tire changes it so much a set checked one day will give a different reading another and so on.....
We always started on lower air and increased until we went too far anyway.
You sell tires, so I see a sales pitch, what I found 8 outta 10 times the harder the tire the stiffer the sidewall
 
CarlsonMotorsports said:
I don't know...
I guess I'll disagree with Jamie again on usefulness of tools.

Burris tires are all over the place on spring rates, even within the same production codes.
While Jamie is absolutely correct in his assertion that the spring pressures vary while on the track, (absolutely they do,) I find it an advantage to know what you are starting with.

We match our tire sets by date code first, then by spring rates. We are primarily interested in right sides matching. I don't even bother with lefts any more. About the only time we check left rears is when we want a stiffer left rear for high cross on big momentum tracks.

Keep in mind that cutting/profiling the shoulder makes a BIG difference in spring rates on a soft sidewall tires, 33s in particular, (not as much on Maxxis, Cobra, Hoosier FK & A40, or Vega Yellow & Blues.)
Most of our 33 stuff doesn't get internally prepped so we don't have to worry about that changing the spring rates. Now, for some of our short track 33 tires that have internal, you can bet that the sidewalls are affected.

Now, consider that you're at a Burris 33 only track: If it's a big momentum track, why would you not want the highest spring rate tires on your kart? It sure beats running higher psi and having to add more prep to get the tire to grip in the corners.
Higher spring rates = roll speed without having to jack the air psi way up.
I find roll speed to ALWAYS be an advantage. That advantage is most easily seen on big momentum tracks, or tracks that bite up good.

It's kind of like the tire temp discussion in another thread on here...
Over emphasis on any one point of data can be misleading. The whole package that has to work together in harmony.

----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
31 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
Click to expand...
Well said.
 
XXX#40 said:
So when you going to spend that grand on a sidewall tester? better run and buy one your program is subpar if you dont own one.
You know what PT Barnum said.......
No thanks I would rather spend that grand on many new tires
Click to expand...
It seems you have a hard time distinguishing between seeing the benefit of something, and having to go out and get one. The benefit is there, even if you dont have the tools to find it yourself.
 
jaymancds said:
It seems you have a hard time distinguishing between seeing the benefit of something, and having to go out and get one. The benefit is there, even if you dont have the tools to find it yourself.
Click to expand...
Well the benefit isnt there with Burris tires, like where this is posted.
Every tack we have ran for the last 12 years is a Burris 33 only tire rule, the benefit is not worth the cost for Burris 33's.
If I ran an open tire rule I might of keep it, but probably not, when buying tires you can ask the tire guys if they have one and can do it for you, and even then 8 time out of ten your hardest duro tires will be a stiffer sidewall
 
Tires are springy and not the springs of your chassis you can use to set a spring rate.

IMHO the answer to the 1st post is yes it sounds right.
When you first see the10 reading for me that's setting a baseline between tires and then you zero.
Next you hat a number at 3/8" for comparison.
A higher number then means when load is applied the stub axle or end of the axle will move down less.
A lower number it will move down more.
Depending on how much difference it could be like moving a washer.
I think especially with right side tires it would be a good thing to know to help in tire selection

All the ranting about other conditions is bull premadona bull.
It's bull because you're putting a number to your tires as they are and all the possibilities of wind he'll and fire out in the world are meaningless.
When track and weather conditions change Duhhh ... They change the same for everyone.



 
Isn't spring rate about how much a spring will compress at various loads?

The tire test per first post Is about what load is needed to compress 3/8" s.

And ??????????
 
KKania17 said:
Why do we scale, corner weights aren’t the same on track, especially if it’s a little rough or if you hop a berm, so why does everyone spend a grand on scales or pay people to scale them? I guess the same logic applies to tires. If there’s a way to buy performance, racers will find a way
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This is the hypocrisy of karting. People say, "There is no benefit in XXX tool because it isnt static on the track." and then turn around and tell you that you need to have an absolutely, positively, perfectly setup scale to have the perfect .1% of weight, even though it doesnt stay the same on the race track. Not to mention holding your body in the perfectly same position through all of the forces of a lap. Its just an indicator of what you need to do. Static measurements are the only baseline we can have for dynamic physics.
 
Thank you to everyone that provided input. As noted, I have access to the equipment at no monetary cost just time. It sounds like I'm using it properly so that's good to know. In terms of the data I gain it sounds like a higher spring rate is preferred. My sample size thus far, RS tires only, align with the comment that 80 - 90% of the time the higher duro equals a higher spring rate. One of the anomaly sets happen to be one of our winningest sets of tires. I tested these tires multiple times to verify results always using the same air pressure. Maybe it's a coincidence but then again maybe it's not.

I'm hoping to hear comments on some of the questions in post 1
 
XXX#40 said:
Well the benefit isnt there with Burris tires, like where this is posted.
Every tack we have ran for the last 12 years is a Burris 33 only tire rule, the benefit is not worth the cost for Burris 33's.
If I ran an open tire rule I might of keep it, but probably not, when buying tires you can ask the tire guys if they have one and can do it for you, and even then 8 time out of ten your hardest duro tires will be a stiffer sidewall
Click to expand...

So I take it you're not having your Burris tires cut either?
You do know that cutting them changes the spring rate, don't you?
I would say that out of ALL of the brands of oval karting tires, you gain the most speed by cutting Burris.
Also there is more variation in Burris, or any floppy sidewall tire in karting (including Hoosier 10,20,30,) than the stiffer sidewall stuff and the all synthetic (plastic) import tires. I can check a case of Maxxis and find very little variation from one right side to another. Same with Vega Yellows.
The exception was the Maxxis EL when they were popular...we saw a very rapid breakdown of the sidewalls after each run - I think that's what ultimately killed the popularity of that tire = fresh sidewalls became necessary...so much for an economy tire.
Also, you can take a hard 33 and cut the shoulders down on it to make it a full round and I guarantee you that it will be a lower spring rate -- AND it makes a difference in how that tire (and ultimately your kart) works on the track.

Not worth arguing with you, Jamie, you don't have to have your tires spring rate tested or use temps. That's just fine. I'm sure you will continue to win plenty of races without doing these things.

Many tire guys sort tires to match them in sets before the customer ever gets them. I suspect that most racers aren't even aware of this being done. The bigger problem with the soft sidewall stuff like Burris is that you really need to match them AFTER they've been cut, not before. Maxxis, and thin rubber stuff that gets relatively little cut (if any) are MUCH easier to sort and match right sides.
There was at least one tire guy who was testing everything that he got in, and keeping back certain sets for himself and his drivers for big races where you knew the track was going to bite up hard. Was it worth it? Maybe...then again, maybe they could have won without all that time and effort.
 
Burris Racer said:
Thank you to everyone that provided input. As noted, I have access to the equipment at no monetary cost just time. It sounds like I'm using it properly so that's good to know. In terms of the data I gain it sounds like a higher spring rate is preferred. My sample size thus far, RS tires only, align with the comment that 80 - 90% of the time the higher duro equals a higher spring rate. One of the anomaly sets happen to be one of our winningest sets of tires. I tested these tires multiple times to verify results always using the same air pressure. Maybe it's a coincidence but then again maybe it's not.

I'm hoping to hear comments on some of the questions in post 1
Click to expand...

On that "anomaly" set, are they cut rounder than the others? The shoulder cut thinner? Maybe flatter with full shoulder?
That definitely affects the spring rate.
See my previous post.
 
CarlsonMotorsports said:
On that "anomaly" set, are they cut rounder than the others? The shoulder cut thinner? Maybe flatter with full shoulder?
That definitely affects the spring rate.
See my previous post.
Click to expand...
I'm not certain on the profile difference. This set of tires were bought used with only a few races on them and were a personal set of the tire cutter.
 
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