Author Topic: FM 158 and 258  (Read 8132 times)

Jerryno

Re: FM 158 and 258
« Reply #15 on: April 27, 2018, 01:05:36 PM »
Wondering if anyone has a 258 in hands and can check if there is flex or smooth operation in the whole travel.

It has to flex, because there is no pivot close or in the real axle.

charlesrg

Re: FM 158 and 258
« Reply #16 on: April 27, 2018, 09:51:34 PM »
Wondering if anyone has a 258 in hands and can check if there is flex or smooth operation in the whole travel.

It has to flex, because there is no pivot close or in the real axle.

So do you think the brake caliper mounted on the seatstay might be an issue ?  This has kept me awake at night for a few days.

bxcc

Re: FM 158 and 258
« Reply #17 on: April 28, 2018, 05:07:53 AM »

Show me one of top 3 podium on World Cup XC race using dropper and you will change me.

Different preferences for different riders but this comment leads me to a couple of questions.
1) are you chasing podiums?
2) have you spent much time on a dropper?

My opinion is that skipping the dropper only because of weight is silly. Sort of like going full rigid because it’s lighter.

sclyde2

Re: FM 158 and 258
« Reply #18 on: April 29, 2018, 05:43:55 AM »
C'mon man, you are sounding like you are joining in on the narrow mindedness.  I.e. Just because something works for you, on the kind of riding/terrain you do, doesn't mean someone else doing the opposite thing is wrong.

I reckon there are xc race courses out there which would warrant a dropper post, not just for more fun, but as a genuine performance enhancer (i.e. increase competitiveness) for the majority of riders, including those with skills of the very elite.

Likewise, there would be courses where the extra weight of the dropper (dunno, about 300-400g?) would be felt too much of the climbs, and not sufficiently compensated on the descents, if they weren't the kind where a dropper helps.

For me, I have been running droppers for over 10 years - started with an original gravity dropper.  On my six inch trail bikes.  But I don't use one on my xc bikes, as the kind of courses I ride only have probably about ~2-3% of track that i would be faster on a dropper.  While I still have at least 5kg that i could lose off me (I might get close by September), I'd rather not be carrying that much unecessary weight on the bike for the other 98% of the course.  Having said that, I have recently been chickening out on a few obstacles, and taking the b line, but that was on my old 26er with 71 degree head angle, longer stem, where the front-tippy feeling moments seemed to be pretty often. 

I reckon we will increasingly find people running droppers on xc race bikes, probably as the weight comes down, and the course features get a bit hairier.  Will be a while for me though - I've now got a new slacker, shorter stemmed, bigger wheelled xc race bike that should get me through even more of the tough bits without feeling that I need stretchier arms and legs to get further back and lower.



bxcc

Re: FM 158 and 258
« Reply #19 on: April 29, 2018, 10:48:20 AM »
C'mon man, you are sounding like you are joining in on the narrow mindedness.  I.e. Just because something works for you, on the kind of riding/terrain you do, doesn't mean someone else doing the opposite thing is wrong.

Is this directed at me? I wasn’t trying to argue with anyone just pointing out the fact that it would be a deal breaker for a lot of people. I totally understand that people like to ride different styles of bike, that’s why I have 3 mountain bikes. But the comments of “get a trail bike if you want a dropper” and “I will run a dropper when the pro’s do” seems a bit off. My question asking if he was chasing podiums was not meant to be sarcastic. I was truly asking to see if they were looking for a dedicated race bike.

charlesrg

Re: FM 158 and 258
« Reply #20 on: April 29, 2018, 01:22:06 PM »
C'mon man, you are sounding like you are joining in on the narrow mindedness.  I.e. Just because something works for you, on the kind of riding/terrain you do, doesn't mean someone else doing the opposite thing is wrong.

Is this directed at me? I wasn’t trying to argue with anyone just pointing out the fact that it would be a deal breaker for a lot of people. I totally understand that people like to ride different styles of bike, that’s why I have 3 mountain bikes. But the comments of “get a trail bike if you want a dropper” and “I will run a dropper when the pro’s do” seems a bit off. My question asking if he was chasing podiums was not meant to be sarcastic. I was truly asking to see if they were looking for a dedicated race bike.

Nah man, the comment was for me. I was being a douche with my comments against dropper. I needed to go for a ride to get more open minded. Did it and I'm now happy with droppers. :P Totally agree, what works for me may not work for others.

sclyde2

Re: FM 158 and 258
« Reply #21 on: April 29, 2018, 07:41:21 PM »

Is this directed at me? I wasn’t trying to argue with anyone just pointing out the fact that it would be a deal breaker for a lot of people. I totally understand that people like to ride different styles of bike, that’s why I have 3 mountain bikes. But the comments of “get a trail bike if you want a dropper” and “I will run a dropper when the pro’s do” seems a bit off. My question asking if he was chasing podiums was not meant to be sarcastic. I was truly asking to see if they were looking for a dedicated race bike.

Yes.  I don't run a dropper on my xc race bike because of the added weight.  So, do you think I'm silly?  As it reads, i can't see any other way to interpret your comment ("My opinion is that skipping the dropper only because of weight is silly").

I would guess that, other than cost/maintenance, the overwhelming main reason people don't put droppers on their xc race bikes is because of weight.  A lot of silly people out there?

As for my contribution to the subject of droppers on these kind of frames, my similar FM058 has a maximum seatpost insertion of 120mm, which would greatly limit dropper post options.  That's on the medium frame, not sure what it is on the other sizes, or what it is on the 158 or 258.  But this measurement shows up on the technical drawing that hongfu supplies before you order.


bxcc

Re: FM 158 and 258
« Reply #22 on: April 30, 2018, 06:33:25 AM »
Yes.  I don't run a dropper on my xc race bike because of the added weight.  So, do you think I'm silly?

If I read only that portion of the comment, then yes, I would think that you are silly. But since I have read all of your other comments on this thread, no I do not think you're silly because there is more to it than weight.

You have a dedicated race bike and you have used droppers in the past so you know what works for you and what doesn't. That is why I asked those questions, "is it a race bike" and "have you used a dropper".

If you read all of my posts in this thread, you will see that I never said it was wrong. I started by saying that the dropper option is nice to have and it seems odd that it would be of modern geometry and not have that option. Then it got confusing with the "Haven't seen any XC racer using droppers and winning races. If you want a dropper why not go for a trail bike or all mountain?" "Show me one of top 3 podium on World Cup XC race using dropper and you will change me." comments. I've used droppers and I know they work for me as they allow me to go faster even on the not so technical stuff all while keeping the optimal seat height during the pedal mashing sections.

I've seen many people stick to skinny rims, rigid posts, and crap tires because that's what the pro's are using and these people are chasing podiums that they may or may not get, and if they do get them, they will never be the bill paying podiums. They are just trying way to hard to play the part.

That being said, now back to our regularly scheduled program.

charlesrg

Re: FM 158 and 258
« Reply #23 on: April 30, 2018, 09:18:48 AM »
In the topic of this frame.

Have you guys noticed that the Brake Caliper sometimes is mounted in the chainstay and sometimes in the seatstay ?

I have an M06 and it's mounted in the chainstay because the seatstay flexes with the wheel travel. If no shock is installed the frame still stays erect, the seatstay acts like a spring.

Wondering if anyone has a 258 in hands and can check if there is flex or smooth operation in the whole travel.



sclyde2

Re: FM 158 and 258
« Reply #24 on: April 30, 2018, 11:04:46 PM »
If you print out a drawing of the frame and draw two circles:
(1) one circle centred on the main pivot, with the circle/arc passing through the pivot at the end of the seat stay.
(2) a smaller second circle centred on the pivot where the linkage is connected to the main frame, with the circle/arc passing through the pivot at the end of the seat stay.

The first circle traces the natural path of the end of seatstay if it wasn't connected to the linkage/rocker.  The second circle traces the path that the linkage/rocker forces the end of the seatstay to take (and forces it to bend).

You can roughly visualise these paths just by looking at it.

The rocker forces the seatstay to bend upwards at first, then down again towards its "natural" path.

I confirmed this on my FM058 frame (with the same pivot locations).  There was initial resistance to compressing the suspension, which eventually went the other way - i.e. around the spot where the shock would bottom out, the "spring" goes the other way, with the seatstay's cross brace suddenly springing towards the seat-tube.
« Last Edit: April 30, 2018, 11:15:39 PM by sclyde2 »

sissypants

Re: FM 158 and 258
« Reply #25 on: May 01, 2018, 02:31:57 PM »
In the topic of this frame.

Have you guys noticed that the Brake Caliper sometimes is mounted in the chainstay and sometimes in the seatstay ?

I have an M06 and it's mounted in the chainstay because the seatstay flexes with the wheel travel. If no shock is installed the frame still stays erect, the seatstay acts like a spring.

Wondering if anyone has a 258 in hands and can check if there is flex or smooth operation in the whole travel.

So I know you've posted around a bit with this question (mtbr and here), and I have the M9007 with this mount, and I have to say I don't really understand what the issue is.  No matter whether the brake is on the seatstay or the chainstay, it's part of the sprung rear triangle, and it's going to affect suspension kinematics under braking equally. When I ride while braking in the rear I don't notice any differences in suspension activity or any lack of braking efficiency.

lRaphl

Re: FM 158 and 258
« Reply #26 on: May 01, 2018, 02:40:52 PM »
I think the problem is the fear that the caliper will move slightly with the flex in the seatstay and change its position relatively to the rear disc.

Jerryno

Re: FM 158 and 258
« Reply #27 on: May 01, 2018, 03:23:37 PM »
Also because the seatstays are thinner one side gets flexed from the breaking forces and the other not. This may be an issue even on hardtails. Some aluminum frames suffer from this and I rarely see a good carbon frame with brake mount in seatstay.

Wirh 160mm rear this is small, but with 180mm the effect is much more.

danK

Re: FM 158 and 258
« Reply #28 on: May 04, 2018, 07:03:24 AM »
So I know you've posted around a bit with this question (mtbr and here), and I have the M9007 with this mount, and I have to say I don't really understand what the issue is.  No matter whether the brake is on the seatstay or the chainstay, it's part of the sprung rear triangle, and it's going to affect suspension kinematics under braking equally. When I ride while braking in the rear I don't notice any differences in suspension activity or any lack of braking efficiency.
Since you brought up suspension, is the shock tune of the aftermarket Fox a great match for the frame's kinematics?
Did you request a firm XC tune?

danK

Re: FM 158 and 258
« Reply #29 on: May 04, 2018, 08:54:43 AM »
158. Looks like 148 only.

https://www.aliexpress.com/item/2018-NEW-29ER-BOOST-Full-Suspension-Full-Carbon-MTB-Bicycle-Frame-FM158-148-12mm/32854553929.html?spm=2114.search0104.3.48.3fb91244sAY1xH&ws_ab_test=searchweb0_0,searchweb201602_3_10152_10065_10151_5722917_10344_10068_10130_10324_10342_10547_10325_10343_5722817_10546_10340_10341_10548_5722617_10698_10545_10697_10696_10084_10083_10618_10307_5722717_10059_5711217_10534_308_100031_10103_441_5722517_10624_10623_10622_10621_10620_5711317,searchweb201603_28,ppcSwitch_5&algo_expid=14ea6170-e624-4ec4-ab4e-da1f802f8f9d-7&algo_pvid=14ea6170-e624-4ec4-ab4e-da1f802f8f9d&priceBeautifyAB=0

258. 142 and 148.

The 258 won't ship till July.

https://www.aliexpress.com/item/2018-NEW-Carbon-Fiber-29er-Full-Suspension-Boost-148MM-MTB-Bicycle-Frame-FM258-UD-Matte/32854379761.html?spm=2114.search0104.3.30.3fb91244sAY1xH&ws_ab_test=searchweb0_0,searchweb201602_3_10152_10065_10151_5722917_10344_10068_10130_10324_10342_10547_10325_10343_5722817_10546_10340_10341_10548_5722617_10698_10545_10697_10696_10084_10083_10618_10307_5722717_10059_5711217_10534_308_100031_10103_441_5722517_10624_10623_10622_10621_10620_5711317-normal#cfs,searchweb201603_28,ppcSwitch_5&algo_expid=14ea6170-e624-4ec4-ab4e-da1f802f8f9d-4&algo_pvid=14ea6170-e624-4ec4-ab4e-da1f802f8f9d&priceBeautifyAB=0

Thoughts on these two frames?
I've never purchased from Aliexpress. The 258 shows 150 frames in stock?! A July delay would be dealbreaker for me. I know you're not the seller, but hoping to get info from anyone regarding what's shown on Aliexpress and what is reality for in stock.