Mechanics Quick Question Thread [Ask Questions Here]

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Mechanics Quick Question Thread [Ask Questions Here]
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flag Nobble
Posted: Jan 23, 2023 at 17:52 Quote
neorider wrote:
how useful are the bleeder ports on fork lowers these days?
It depends where you ride. If you travel across a big elevation change up to a bike park or something then they’re amazing. For example when I go to Northstar I’m going from nearly sea level to approximately 6500ft. The fork feels noticeably worse when you get there. We used to stick a zip tie past the seal to let the air out. Bleeders let you fix that with a quick button press.
flag Lion1
Posted: Jan 23, 2023 at 18:06 Quote
Do any of you guys have experience with the DVO Topaz 2 rear shock? I would like to put one on my Evil Following but I am unsure how it will perform with the high leverage ratio of my bike and I have heard some people say it has durability issues compared to the Topaz 3.
flag KennysWorld
Posted: Jan 23, 2023 at 21:45 Quote
Commencal Meta HT AM:

Trying to install rear Magura MT5 (4-pot). 180mm rotors don't allow clearance for caliper. Learned I will have to upgrade to 203mm rear rotor. What brake adapter do I need?
flag Bcriswell
Posted: Jan 24, 2023 at 9:52 Quote
I just got a great deal on a set of 2022 SRAM G2 RS brakeset. I will be using all new hose and fittings but I am conflicted on what to use due to what I have read and seen online. While viewing the official SRAM service manual, I can see they use the red stealthamajig fitting with the hose barb being silver with a lip on it. There is also another hose kit that was recommended by WWC (via online chat) that includes silver olives (look the same as the red so assume they are the same) but the hose barbs are black and do not look like they have lip on it. Both links below. Can someone for the life of me please tell me which fittings are specifically for the G2 line of SRAM brakes? Thank you in advance for any insight you can provide. It's not that I don't trust the guys at WWC, but I don't know why the manual shows different fittings.


https://www.jensonusa.com/SRAM-Guide-Hydraulic-Line-Kit (kit that looks identical to the G2 service manual pictures)

https://www.jensonusa.com/SRAMAVID-Hydraulic-Line-Kit (kit is almost identical to the one above, but the barbs look different.)
flag blamalamadingdong
O+
Posted: Jan 24, 2023 at 11:46 Quote
KennysWorld wrote:
Commencal Meta HT AM:

Trying to install rear Magura MT5 (4-pot). 180mm rotors don't allow clearance for caliper. Learned I will have to upgrade to 203mm rear rotor. What brake adapter do I need?

these bikes come with 180mm rotors you either mounted something wrong or something else is questionable. I would double check you have the ISG mount on correctly and the spacer on correctly.
flag Nobble
Posted: Jan 24, 2023 at 12:28 Quote
Bcriswell wrote:
I just got a great deal on a set of 2022 SRAM G2 RS brakeset. I will be using all new hose and fittings but I am conflicted on what to use due to what I have read and seen online. While viewing the official SRAM service manual, I can see they use the red stealthamajig fitting with the hose barb being silver with a lip on it. There is also another hose kit that was recommended by WWC (via online chat) that includes silver olives (look the same as the red so assume they are the same) but the hose barbs are black and do not look like they have lip on it. Both links below. Can someone for the life of me please tell me which fittings are specifically for the G2 line of SRAM brakes? Thank you in advance for any insight you can provide. It's not that I don't trust the guys at WWC, but I don't know why the manual shows different fittings.


https://www.jensonusa.com/SRAM-Guide-Hydraulic-Line-Kit (kit that looks identical to the G2 service manual pictures)

https://www.jensonusa.com/SRAMAVID-Hydraulic-Line-Kit (kit is almost identical to the one above, but the barbs look different.)
look at your caliper, that should make it clearer what you need. I believe it’s the first one.
flag neorider
Posted: Jan 24, 2023 at 12:43 Quote
BenLow2019 wrote:
blamalamadingdong wrote:

correct. for refence, TWE is 3400m elevation. the base is 1200m elevation. even tire pressure felt a bit out at the top. for what its worth, my friend had no bleeders and he was fine. so to answer your question, if you wanna save money, skip the bleeders.

Tire pressure can feel very different between two significant elevations: high elevation the tire will feel hard; lower elevation the tire will feel soft.
The rubber of the tire will expand as the force of the atmosphere against it is reduced at higher elevation. The tire tire will collapse as you descend in elevation and the atmospheric pressure increases.

It was most likely the effect on the tires that made you think the fork felt crappy.

The same effect also happens on the fork but the surface area of the fork is smaller than the tires.
One or two thousand feet difference at a bike park you probably can't tell the differences because the total pressure difference is about 5 psi between sea level and 10,000 feet. TWE starts at about 10,500 feet and descends to about 4000 feet - that's over 6000 feet different. If you set your bike up at sea level and then shuttled up to the top of TWE you would definitely need to let a little air out of the tires and a touch of air from the fork.

I thought air pressure is lower at higher elevation ? lol I get it but still confused
flag blamalamadingdong
O+
Posted: Jan 24, 2023 at 14:15 Quote
neorider wrote:

I thought air pressure is lower at higher elevation ? lol I get it but still confused

atmospheric pressure is lower at altitude. less pressure outside means more inside
flag RelapsedMandalorian
Posted: Jan 24, 2023 at 15:05 Quote
Significant annoyance: bearing change on a 2020 RM Slayer, when I tighten the chainstay/seatstay bolts to the recommended torque (17nm), it becomes too stiff to move freely, what am I missing?
flag BenLow2019
Posted: Jan 24, 2023 at 16:56 Quote
blamalamadingdong wrote:
neorider wrote:

I thought air pressure is lower at higher elevation ? lol I get it but still confused

atmospheric pressure is lower at altitude. less pressure outside means more inside

Take a balloon from sea level to 10000 feet and you can see it will get bigger.
Look at bags of potato chips at the grocery store when you're at a higher elevation and the bags look big and puffy. The same bags at sea level will look deflated or normal.
The air trapped inside the balloon and the bag of chips is pushing outward and the atmosphere is pushing inward against the outside of the balloon or the bag. Since the atmosphere has a lower pressure at a high altitude then the balloon and the bag will seem to inflate by themselves. Here's a video.

Bike tires do the same thing - they will feel much harder at higher elevation because the atmosphere isn't pushing against the outside as much as it does at sea level. So if you shuttle up to a higher altitude after setting your bike up at sea level you will want to release a little air from the tires to make them feel okay.
flag gabriel-mission9
Posted: Jan 25, 2023 at 2:30 Quote
I think the altitude/pressure change thing is being blown slightly out of proportion. As stated above, sea level to 10'000ft is about 5 psi, and the higher from sea level you start the less the pressure drops as you rise (eg the pressure difference between 50'000 ft and 60'000 is around 1psi)

Even on an extraordinarily long mtb descent you are unlikely to see a pressure differential of more than 1-2 psi as you descend, and correcting at the top, only means it'll be incorrect by the bottom. Champerey (a relatively steep and long descent that has been used on the dh race circuit) drops about 1000ft over its length. You might want to let 0.25psi out of your tyres/suspension at the top, if you are truly concerned about the negative effects any pressure difference may cause.
flag gabriel-mission9
Posted: Jan 25, 2023 at 2:42 Quote
RelapsedMandalorian wrote:
Significant annoyance: bearing change on a 2020 RM Slayer, when I tighten the chainstay/seatstay bolts to the recommended torque (17nm), it becomes too stiff to move freely, what am I missing?

Likely either:
a) a spacer missing somewhere, meaning when you torque down the bolts two moving parts are coming into contact where they shouldnt be, or
b) a bearing not sitting perfectly straight in its bore, meaning it gets pulled at an angle when torqued down.
flag Pizzocchero62
Posted: Jan 25, 2023 at 5:24 Quote
Dirt jump/single speed related question

I've got this DJ frame with horizontal dropouts ( DMR Sect ), rear hub is a DT Swiss 440/Magura FR currently set up as 10mm QR ( 5mm skewer).

I'm having issues with the wheel not being tight enough so it is slipping and moving forward in the dropouts.
I've tried with a couple of different qr skewers, some crappy ones and a Shimano one, with the Shimano I managed to tighten it up enough so that I can at least pedal around but I very worried about jumping.

Is it worth try with some bolt on skewers? will they provide a stronger clamp? in the UK i'm only finding the Halo one which are not recommended for off road use.

The other option I've seen is to convert the hub to through bolt ( 135x10 or 135x12 ) but I couldn't find a lot of info online about it and which would work with my setup.

What's my best option ( aside from getting a new rear wheel with bolt on nuts, which is out of question cause I can't afford )?
flag gabriel-mission9
Posted: Jan 25, 2023 at 6:24 Quote
Pizzocchero62 wrote:
Dirt jump/single speed related question

I've got this DJ frame with horizontal dropouts ( DMR Sect ), rear hub is a DT Swiss 440/Magura FR currently set up as 10mm QR ( 5mm skewer).

I'm having issues with the wheel not being tight enough so it is slipping and moving forward in the dropouts.
I've tried with a couple of different qr skewers, some crappy ones and a Shimano one, with the Shimano I managed to tighten it up enough so that I can at least pedal around but I very worried about jumping.

Is it worth try with some bolt on skewers? will they provide a stronger clamp? in the UK i'm only finding the Halo one which are not recommended for off road use.

The other option I've seen is to convert the hub to through bolt ( 135x10 or 135x12 ) but I couldn't find a lot of info online about it and which would work with my setup.

What's my best option ( aside from getting a new rear wheel with bolt on nuts, which is out of question cause I can't afford )?

What year is your frame?

The current Sect uses taper lock dropouts, and should not slip if done up tight.
https://www.dmrbikes.com/Catalogue/Components/Dropouts-click-here-to-preview/Taper-Lock-Washers

Older Sects may not have used taperlock dropouts. I don't know. You are probably best off contacting DMR and asking. They are cool guys and will be happy to help


*edit* ah, ive had a closer look and DMRs taper lock design is not gonna play nice with qr hubs. Your best bet really is gonna be a proper nutted axle dj hub. If you cant afford this then you are gonna have to convert it to 10x135 and throw some 10mm threaded bar through the middle with nuts on the end. Bit of a bodge, but it'll work. (I used to have a very similar setup on my DMR trailstar back in the 90s when qr hubs were pretty much the only option.)
flag Pizzocchero62
Posted: Jan 25, 2023 at 7:44 Quote
It's a 2019 model, I bought it used and didn't came with the taper lock washers so I'm not sure it's been designed for them. I'll email DMR anyway.

I was thinking about the threaded bar bodge, I'm even thinking about going full ghetto and drill the qr hub caps hole to fit a 10mm bar!

Thanks for answering btw!

 


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