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602
Joined
10/26/2006
Location
Atl, GA, USA
Edited Date/Time
11/8/2022 9:02am
HRC Team Gariboldi (MXGP Honda Team) posted an Instagram story showing the mechanics cleaning Tim Gajser's 2022 HRC CRF450RW parts...
During the video there is a quick shot of the HRC clamps getting cleaned. I noticed an unusual "groove" inside the clamp. This groove goes around the complete circumference. Not to be confused with the usual "groove" HRC clamps have going vertical (used for a shim if needed to reduce the diameter).
HRC clamps with normal vertical groove for the shim
HRC clamps with new circumference "groove". This is a screenshot... best I could do.
I know Team Honda USA with Sexton and Roczen used the Xtrig split clamps for a couple of races then went back to the HRC clamps. Perhaps they went back to the HRC clamps because they now have their own version of "split" clamps?
... or I could be totally off base and that's not a groove, idk.
Side note... new this year to HRC Honda MXGP Team is the branding of "Talon" on their hubs and triple clamps. All though these parts are "Talon" branded they are indeed full works parts. Not off the shelf Talon parts. HRC doesn't actually make anything... They design and then contract the work out to vendors.
Team Honda in the States for example has used Hinson to make their works clamps in the past along with other parts.
During the video there is a quick shot of the HRC clamps getting cleaned. I noticed an unusual "groove" inside the clamp. This groove goes around the complete circumference. Not to be confused with the usual "groove" HRC clamps have going vertical (used for a shim if needed to reduce the diameter).
HRC clamps with normal vertical groove for the shim
HRC clamps with new circumference "groove". This is a screenshot... best I could do.
I know Team Honda USA with Sexton and Roczen used the Xtrig split clamps for a couple of races then went back to the HRC clamps. Perhaps they went back to the HRC clamps because they now have their own version of "split" clamps?
... or I could be totally off base and that's not a groove, idk.
Side note... new this year to HRC Honda MXGP Team is the branding of "Talon" on their hubs and triple clamps. All though these parts are "Talon" branded they are indeed full works parts. Not off the shelf Talon parts. HRC doesn't actually make anything... They design and then contract the work out to vendors.
Team Honda in the States for example has used Hinson to make their works clamps in the past along with other parts.
For sure there is a pupose for the groove, it's for flex.
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The steering stem of those HRC clamps appears to be an OEM aluminum part vs the HRC titanium stem.
HRC triple clamps have used in the past a titanium stem with smaller diameter. The reason for the smaller diameter vs OEM size wasn't done for weight savings. It was done to allow the use of smaller diameter bearings. Therefore, providing room (within the head tube) to use eccentric bearing races. Allowing the change of rake.
Here is a picture of my HRC clamps with titanium stem (small tube and bearings) and the HRC bearing/races (these races are for stock rake on a 2016 CRF450R)
One would have to believe the groove would also in some way affect the handling of the motorcycle (at least something noticeable to an elite rider). Heck these guys (top factory level racers) notice a change in handling with different chamfers on the top and bottom outside circumference the clamps.
The HRC groove just seems to small and deep for just weight savings. To deliberate in its design. HRC really just doesn't strike me as a company that would modify their existing clamp design, a design they have used for many many years, to just save a minuscule amount of weight. In others words... That weight savings "option" of a inner groove has always been there... why didn't HRC use it before? I believe it must also have other "benefits".
Perhaps HRC is providing their own solution (in a covert manner) to what KTM does with their Factory clamps.
The picture below is of Antonio Cairoli bike (picture by Michael Lindsay). Basically the HRC clamp but in "reverse"?
Changes in the stiffness of the fork tube can indeed be very noticeable, as it can reduce the bushing binding if done correctly. In all cases, a fully split lower clamp will be better than a solid clamp (or partially split clamp) to reduce bushing binding (see this blog post: https://www.luxonmx.com/blog-luxon-split-triple-clamps-flex-advantage.h…). Note that a split upper clamp has no effect on the overall feel of the bike. That’s because it’s not in an area where the bushing travels and it’s clamping around an essentially solid cylinder (the fork tube with the cap threaded into it). And that’s why the Luxon top clamps are not fully split. They’re actually much like the Honda clamps in this thread. The interior relief cut helps to isolate the bolt torque slightly and reduces weight while maintaining (relative) ease of machining and a spot for branding.
This week’s pit bits is pretty good at showing the different “split” clamps that KTM is running. No one on the team is running the full split of the KTM powerparts/factory triple clamps that you can buy. Both Dungey and Plessinger are running the clamps with a split, but they’re joined together again at the pinch bolts. The standard powerparts/factory triple clamps are split all the way through. Cairoli is running the same clamps, but without any of the split. Note that the KTM clamps don’t have custom outer profiles or anything. Of the three variations, they’re all the same; the only difference is whether the splitting operation is done (or how much of it is done) in the machining.
The outer profile of the fork tube clamp on KTM triple clamps the will be beneficial to the bushing binding to some extent, split or not. But if it’s split, it will be dramatically better at reducing the binding than if it’s not split. The Honda being the opposite (relief on the inside) will have the least effect on reducing bushing binding, and by a massive margin at that. So much so, that is may as well not be there at all. If Honda was really looking to make a change in feel for the riders, they would have put the relief on the outside of the clamps.
It's obviously hard for mechanical engineers to understand the extrinsic value of such things (the groove).. but that's the beauty of this sport. Riders can feel what the engineers cannot measure. And the great teams rely on this.
The feel is very noticeable to these elite riders. With Tim Gajser just winning the MXGP title and Sexton kicking ass, it's pretty good evidence HRC knows what they are doing.
Looking at this photo (zoom in and squint 😁) you can see what appears to be a groove inside the top triple clamp. The same type of groove seen in the pictures, I posted earlier, of the bottom MXGP HRC triple clamp.. (photo credit..I forget where I got it, sorry)
Same photo zoomed in and enhanced for the lazy
The riders haven't found some magical change that mystifies engineers. The mind is a powerful thing, and if a rider knows that there's a "change", they will most certainly feel it, whether it actually changed anything or not.
In my last post, I explained exactly what the "groove" was intended to achieve (suspension/feel) for the Rider.
The first version of the HRC billet triple clamps had square edges. One of the things HRC found was that by beveling the edges of the clamps with a file, it would soften the feel in the front. I am not sure I would feel such a minor change, but apparently the factory riders did. The next version of the HRC clamps came with the beveled edges which then evolved to a third version with rounded edges. A lot of riders where also not fans of the bigger 51mm fork tubes and preferred the previous Showa for with 49mm tubes or later on, even the Kayabas with the 48mm tubes. Initially HRC had triple clamps to accommodate each of these fork sizes to allow riders to find a fork tube size that worked for them, however, it was becoming expensive and inconvenient for the teams to keep so many different triple clamps sizes for each of the steering offsets they also provided to suit rider preferences. That is when HRC started to provide triple clamps machined to accept a shim to be able to use the same clamps for a smaller tubed fork. HRC's offset steering bearings also helped in minimizing the number of different clamps that factory teams needed to keep on hand.
Here are some pics of an HRC offset steering bearings. Notice how the HRC steering bearings are taller than the OEM bearing, in the first pic, so the smaller diameter HRC titanium stem was not a weight savings measure, but allowed for the use of the concentric bearings to change steering offset.
It seems clamp design and fork tube size has continued to evolve with riders seeking flexier clamps with the newer split band design becoming popular and factory fork tube preferences moving away from the biggest tube sizes back down to 48 and 49mm lower tubes as the optimal trade-off between rigidity (to minimize fork binding and deflection) and compliant feel.
Most recently we seem to be seeing HRC factory riders experimenting with swapping out the billet parts for forged cast such as the clamps and fork lugs. I found all this evolution in parts interesting.
Pit Row
And if it's measured to be REALLY small, then the change in feel will also be REALLY small. Often times, it's so small that the change is overwhelmed by everything else that's flexing on the bike.
Back to back testing of the changes is great. But the time delay between tests is enough to change the tire pressure 0.25 psi, which will make a 100x more of a difference in feel than adding a small chamfer on the triple clamp. Or the track may dry out a bit, making the tests inconclusive. Or any of the other many variables out of our control can change.
Test riders are incredibly valuable, as all the calculations in the world can only go so far. However, test riders, and track testing in general, are full of faults and uncontrolled variables. Gathering test rider feedback, while understanding those faults, AND understanding the engineering calculations behind a design are the keys to going faster.
Simply listening to rider feedback wile ignoring everything else will have you chasing setups all season long. As a mechanical engineer who's spent 1000s of hours analyzing and testing various triple clamp designs, I know very well what changes will be completely un-noticeable on the track, and which ones might make a real difference. If the test rider comes back saying they do notice something that should have no effect whatsoever, then we need to understand why. Are they noticing something else that also changed (track conditions, air pressure, etc., there's a huge list)? Are they just a bad tester (many big names suck at testing, while others are really good)? Was something missed in the engineering?
Once you can minimize the testing variables and have a great test rider, then you can try to sort out the on-track value (or failure) of real engineering changes to a design. It's not just about what the rider feels, it's the whole package.
What if you know that you've made changes to a triple clamp design that had 100x or more the difference than the above mentioned change, AND that it was tested by multiple top professional riders who did not notice any change in feel. Wouldn't it be safe to assume the first mentioned change, the one many order of magnitudes smaller, also couldn't be felt? If you disagree, please explain why.
That's engineering; understanding why a change makes a difference in feel and why another would not. Designing is making a change based on a guess (or just copying something else) and relying on the test rider to tell you if it made a difference or not. The designer largely does not understanding why things are changing. Many things are designed in this industry rather than engineered.
Second, I have a question: are the fork tube bores on triple clamps supposed to be the same diameter, the entire length? Like an engine cylinder? Or do manufacturers "ovalize" them with smaller IDs at the top and bottom?
Reason I ask is this: I am swapping some shorter offset triples onto a KTM 500 EXC. I did the same on an earlier KTM and liked the feel quite a bit, so I am going to play with less offset / more trail on this bike. No one makes new shorter triples, so I purchased two sets on EBay.
I was going through them cleaning up the threads, etc. While doing this I thought I would lightly run a hone through the bores to add some roughness (the slightest drop tweaks the alignment) and sorta clean them up. When I ran the hone through it was clear the stones were contacting more at the top/bottom and less in the center. Is that normal?
Pics:
I ran the hone for 20 secs and understand that the finish needs to be finer. If you look you it appears the contact areas are uneven. Is that normal or incorrect? Should I not have done this? FYI I am now having them anodized with is supposed to add a couple thousandths back to the ID. Should they be left alone afterwards or hone them again? Lottery is $1.8B, do you have the winning numbers?
Jokes aside, it would be great to hear your insights on this.
Thanks,
BP
I'm mainly interested in what Luxon has to say though.
BP
I can see a typical DIY engine cylinder honing tool, either the scraper or toilet-brush style ones, not being reliable when it is used in such a shallow 'cylinder', as the sections of triple clamp are.
But I don't know shit, so as you were 👍
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